All of these apps are very small, I think the biggest is XBMC, you should have no problem installing them all on a stock 8gb.
-dvd2xbox
Popular program used to backup discs.
-linux
I wouldn't bother, if you are going to use it, you might as well devote a whole box to it.
-kai
Installed on the PC, allows you play System Link games over the net.
-further app- (evox etc)
I keep Evox around, always good to have a backup, plus it has trainer support.
-more skins
Just find one you like
-xbox media centre 1.1.0
Get whatever the current build is and find a skin you like.
-cinfig magic
Never actually used it.
-dvdx2
This allows you to play DVDs without the $30 Remote
-other (please specify with details)
Complex Tools v1.6 - Another great utility to backup games. It can also unpack rar and iso files.
Linksboks - web browser, if you are into that.
Emulators - Old school games are small, especially from systems like NES, I'm talking 256kb per title.