Here is a rundown of stuff I use
Web: Firefox (duh)
Email: Evolution (now that I finally found a good tutorial to get spam filtering working. It was so easy I feel stupid for missing it)
IM: Gaim (although I only use google talk)
Scripting editor: Bluefish (I use it for all php, html, and other scripting projects)
Notepad/text editor and mild programmign editor: Gedit
Map software: Google earth linux beta
VNC/RDP client: Terminal Server Client (comes with ubuntu by default)
Office: Open office. My wife uses abiword and gcalc instead of open office.
Video editing: Kino
Video playing totem-xine (Plays everythign I've thrown at it, including dvd's)
Video playing in web browser: Totem-browserplugin
Music: Rythembox (its good enough, although I wish it had an EQ)
Games (native): UT2004, Doom3, Quake4, freespace 2, X2: The threat, Neverwinter nights, Battle for wesnoth, ufoai, and other open source games.
Games (cedega): Steam, guildwars, starcraft, bualders gate 2, Icewind dale 2, Battlefield 2.
DVD/CD burning: I use the built in functions in gnome for ripping iso's and burning iso's. I find an actual app is not really needed for my needs.
DVD ripping: xdvdshrink (download the rpm and run it though alien to make a deb, works perfect).
There is a ton of posts in the ubuntu forums covering this in great detail.