I just install the base KDE making sure that ktorrent, xchat, thunderbird, amarok and kaffienne are installed along with the kernel development packages. I also install the AMD codeanalyst, AMD perfomance library , framewave, maya and Pro/E.
Well, with any new install of any distribution, these are the applications I grab right after a fresh install: VLC and codecs, Gimp (If already installed I grab plugins too.), Pidgin, flash and ktorrent.
If its Debian or Ubuntu I will install dash, and go to /etc/inittab and remove some of the extra terminals. I will also grab screen as well.
Then I'll grab a few games too:
X-moto, Wesnoth, Supertux 2, Nexuiz, Urban Terror.
Once my games and applications I want are in, I go digging for wallpapers, I usually use Bit Torrent to get a pack of those.
Then I might install some non-free games like Quake 3 and UT 2004.
Theres more stuff I do but this is the stuff that comes to mind.