This page is a basic overview of what makes up Ubuntu Studio.
ubuntustudio-desktop

acpi, acpi-support, acpid, alacarte, anacron, apmd, apport-gtk, avahi-daemon, bc, bug-buddy, cdparanoia, cdrecord, contact-lookup-applet, cupsys, cupsys-bsd, cupsys-client, cupsys-driver-gutenprint, dc, deskbar-applet, desktop-file-utils, doc-base, dvd+rw-tools, ekiga, eog, esound, evince, evolution, evolution-exchange, evolution-plugins, evolution-webcal, file-roller, firefox, firefox-gnome-support, foo2zjs, foomatic-db, foomatic-db-engine, foomatic-db-hpijs, foomatic-filters, fortune-mod, gaim, gcalctool, gconf-editor, gdebi, gdm, gedit, gnome-about, gnome-app-install, gnome-applets, gnome-control-center, gnome-cups-manager, gnome-icon-theme, gnome-keyring-manager, gnome-media, gnome-menus, gnome-netstatus-applet, gnome-nettool, gnome-panel, gnome-pilot-conduits, gnome-power-manager, gnome-session, gnome-spell, gnome-system-monitor, gnome-system-tools, gnome-terminal, gnome-themes, gnome-utils, gnome-volume-manager, gnome2-user-guide, gs-esp, gstreamer0.10-alsa, gstreamer0.10-esd, gstreamer0.10-plugins-base-apps, gthumb, gtk2-engines, gucharmap, hal, hal-device-manager, hotkey-setup, hwdb-client-gnome, landscape-client, language-selector, lftp, libgl1-mesa-glx, libglut3, libgnome2-perl, libgnomevfs2-bin, libgnomevfs2-extra, libpam-foreground, libpt-plugins-v4l, libpt-plugins-v4l2, libsasl2-modules, libstdc++5, libxp6, metacity, min12xxw, mkisofs, nautilus, nautilus-cd-burner, nautilus-sendto, notification-daemon, pnm2ppa, powermanagement-interface, readahead, rss-glx, screen, screensaver-default-images, scrollkeeper, serpentine, slocate, smbclient, ssh-askpass-gnome, synaptic, tangerine-icon-theme, tango-icon-theme, tango-icon-theme-common, tomboy, totem, totem-mozilla, tsclient, ttf-bitstream-vera, ttf-dejavu, ttf-freefont, ubuntu-docs, ubuntu-sounds, unzip, update-notifier, usplash, usplash-theme-ubuntu, vino, wvdial, x-ttcidfont-conf, xkeyboard-config, xorg, xsane, xscreensaver-data, xscreensaver-gl, xterm, xvncviewer, yelp, zenity, zip
ubuntustudio-audio

All applications deemed nessessary to provide a working PC studio environment. This is the package most users of other derivatives will be interested in, so they don't get forced into a different desktop environment with a new theme and such.
Package list:

aconnectgui alsa-tools alsa-tools-gui audacity ardour2-gtk beast bitscope creox denemo timemachine gtick hydrogen jackbeat jackd jackeq jack-rack jack-tools jamin jdelay lilypond lilypond-data meterbridge muse patchage qamix vkeybd qjackctl puredata rosegarden4 timidity seq24 shaketracker sooperlooper swami csound tapiir freqtweak mixxx terminatorx xmms xmms-jackasyn xmms-modplug zynaddsubfx fluidsynth bristol freebirth qsynth tk707 linuxsampler linux-image-lowlatency

* Also the linux-image-lowlatency kernel will be installed by default but will not be a depend of the meta. So you can remove it if you use a custom kernel and wont break the meta.

Description:

* aconnectgui - graphical ALSA sequencer connection manager
* alsa-tools
* alsa-tools-gui
* audacity - Swiss army audio editor
* ardour - Digital audio workstation (graphical gtk interface)
* beast - music synthesis and composition framework
* bitscope - diagnosis tool for JACK audio software
* creox - real-time guitar effects
* denemo - A gtk+ frontend to GNU Lilypond
* timemachine - JACK audio recorder for spontaneous and conservatory use
* gtick - Metronome application
* hydrogen - Simple drum machine/step sequencer
* jackbeat - audio sequencer
* jackd - JACK Audio Connection Kit (server and example clients)
* jackeq - routes and manipulates audio from/to multiple sources
* jack-rack - LADSPA effects "rack" for JACK
* jack-tools - various JACK tools: plumbing, play, udp, ctl, scope, clock
* jamin - Audio mastering from a mixed down multitrack source with JACK
* jdelay - A small command line JACK app you can use to measure the latency of your sound card.
* lilypond-data - LilyPond music typesetter (data files)
* lilypond - A program for typesetting sheet music
* meterbridge - A collection of Audio meters for the JACK audio server
* muse - Qt-based midi/audio sequencer
* patchage
* qamix
* vkeybd - Virtual Keyboard program
* qjackctl - User interface for controlling the JACK sound server
* puredata - realtime computer music and graphics system
* rosegarden4 - music editor and MIDI/audio sequencer
* timidity - Software sound renderer (MIDI sequencer, MOD player)
* seq24 - Real time MIDI sequencer
* shaketracker - MIDI sequencer with tracker GUI
* sooperlooper - Looping Sampler LADSPA plugin
* swami - SoundFont editor
* csound - powerful and versatile sound synthesis software
* tapiir - A tool for real time audio delay and feedback effects
* freqtweak - Realtime audio frequency spectral manipulation
* mixxx - A digital DJ interface (for beat-mixing)
* terminatorx - A realtime audio synthesizer
* xmms - Versatile X audio player that looks like Winamp
* xmms-jackasyn - JACK Output plugin for xmms
* xmms-modplug - ModPlug plugin for XMMS
* zynaddsubfx - Realtime software synthesizer for Linux
* fluidsynth - Real-time MIDI software synthesizer
* bristol - vintage synthesizer emulator
* freebirth - Bass synthesizer/sample player/sequencer similar to Rebirth
* qsynth - fluidsynth MIDI sound synthesiser front-end
* tk707 - drum sequencer for a sound card or MIDI device
* linuxsampler - software audio sampler
* wired - A professional music production and creation free software running on the Linux operating system.
* linux-image-lowlatency - Low latency kernel ubuntustudio-plugins

A plug-ins package.

Package list:

blop caps cmt fil-plugins ladspa-sdk mcp-plugins omins swh-plugins tap-plugins vcf-plugins dssi-example-plugins dssi-host-jack dssi-plugin-fluidsynth dssi-plugin-hexter dssi-plugin-hexter dssi-plugin-xsynth dssi-utils
Description:

* blop - Bandlimited wavetable-based oscillator plugins for LADSPA hosts.
* caps - A collection of refined LADSPA plugins.
* cmt - (Computer Music Toolkit) A collection of LADSPA compatible plugins.
* fil-plugins - Parametric equalizer LADSPA plugin.
* ladspa-sdk - Sample tools for linux-audio-dev plugin architecture.
* mcp-plugins - LADSPA plugins designed for Alsa Modular Synth.
* omins - Collection of LADSPA plugins geared at modular synthesizers.
* swh-plugins - Steve Harris's LADSPA plugins.
* tap-plugins - Tom's Audio Processing LADSPA plugins.
* vcf-plugins - Audio EQ biquad filter LADSPA plugins.
* dssi-example-plugins - Example DSSI plugins.
* dssi-host-jack - An example DSSI host.
* dssi-plugin-fluidsynth - Soundfont player/synth for DSSI.
* dssi-plugin-hexter - A Yamaha DX7 modeling software synthesizer for DSSI.
* dssi-plugin-xsynth - A classic-analog style softsynth DSSI plugin.
* dssi-utils - Command-line utilities for sending commands to DSSI plugins.

ubuntustudio-video

Video editing apps.

Package list:

pitivi cinepaint ffmpeg ffmpeg2theora kino stopmotion synfigstudio dvgrab
Description:

* pitivi - Video editor
* cinepaint - A painting and image retouching program designed to work best with 35mm film and other high resolution high dynamic range images.
* ffmpeg - Multimedia player, server and encoder
* ffmpeg2theora - Theora video encoder using ffmpeg
* kino - A non-linear editor for Digital Video data
* stopmotion - A program for creating stop motion animation.
* dvgrab - Grab digital video data via IEEE1394 links

jahshaka - (not in the repos and deferred until next upstream release.)
cinelerra - (not in the repos and deferred until license issues are worked out)

ubuntustudio-graphics

A current, complete set of 2D/3D manipulation applications. ie: Inkscape, GIMP, Blender, and so on.

Package list:

inkscape blender gimp gimp-gap gimp-svg gimp-dcraw f-spot scribus fontforge gnome-raw-thumbnailer xsane wacom-tools hugin agave yafray
Description:

* inkscape - A vector-based drawing program.
* blender - A very fast and versatile 3D suite for modeling, animation, rendering, post-production, interactive creation and playback.
* gimp - A raster-based drawing program.
* gimp-gap - GAP is a collection of plug-ins to extend the GIMP with capabilities to edit and create animations and movies as sequences of single frames.
* gimp-svg - A plug-in to import SVG images.
* gimp-print - Print plugin for the GIMP
* gimp-ufraw - A plug-in to import RAW images.
* f-spot - A personal photo management application.
* scribus - A open source desktop page layout program.
* fontforge - Font Editor for PS, TrueType and OpenType fonts.
* gnome-raw-thumbnailer - a thumbnailer for GNOME that will make thumbnails for camera RAW files.
* xsane - GTK+-based X11 frontend for SANE. (Scanner Access Now Easy)
* wacom-tools - Software for you Wacom drawing pad.
* hugin - An easy to use cross-platform GUI for Panorama Tools.
* synfigstudio - A vector 2D based animation package (GUI)
* agave - Colorscheme generator.
* enblend - A tool for compositing images.
* yafray - A modern, xml-speaking raytracing-based rendering system
* nautilus-image-converter - nautilus extension to mass resize images