ableton live is the greatest thing ever, but they prefer that you pay them.
here's a list of freeware and shareware sampling programs. there are tons of free samples floating around on the internet (
here's a decent list).
you could also get a free program that can host vst instruments or plugins like
cantabile. there are a fair amount freeware vst insruments out there (just google "free vst instruments"). there are a lot of free vst effects plugins--
mda makes an assload.
if you need to mix together any tracks, or edit any wav files,
audacity is the shit.
like splates said, most of the free stuff out there is pretty limited. you can still get creative with it, but it'll take lots work to do something a professional piece of software could do in minutes.