knoppix is definitely my fave live-distrib OS
of course, as in the case of any of-removable-media OS you need lotsa RAM to run it at some reasonable speed (i mean enough RAM to load all progs, w/o necessity to load stuff from CD during the work), but having the OS always with you anywhere you need it is really worth it
knoppix has been the only unix-based OS i've been using before i bought another harddisk for freebsd... simply "grande" ;-) and has everything you might need...
btw. it's a good choice also for the "noobs" to the world of unix, as you don't log in as admin, but just user, so you can't destroy so much