I tend to run mostly Dungeon magazine stuff so I don't have much need for character generators. What I do use:
For face to face gaming:
DM's Familiar (my program): Combat management to track initiative, spell durations, roll hit points, and rolling all the attack/damage. Instant rules lookup. Has all of the world/campaign/adventure notes in it.
Tablesmith: For rolling up random stuff, mostly flavor text - what's the bartender's name and a description, what's the inn serving for lunch today, description for the magic wand the party just found.
Schtuff Wiki: I maintain a wiki on schtuff for the campaign. I frequently update that during the game to record major happenings.
My Campaign Wiki
For online gaming:
Klooge.werks : Allows all the players to connect up, displays the map and tokens, plays sounds, manages combat, does the dice rolling for all the players and the DM's, stores character sheets. A very powerful program that is great for online play and really removes the drugery from the game. I find playing online with klooge to be better than face to face games.
DM's Familiar : Don't need the combat management with klooge, but I still use it to lookup rules and to keep my notes.
Tablesmith: Same as above
Ventrilo: For voice chat
Dunjinni: If I need to make a map myself.
Gimp: To edit maps I scan in
SnagIt: For screen captures. For example, I scan a lot of Dragon/Dungeon magazine and use SnagIt to grab a face in a picture to use for an NPC.