Acid Pro is quite good. I think version 4 was the best and easiest one (while it was still made by Sonic Foundry). Sony got a hold of it from version 5 onwards (now at version 7) and has ruined it in my opinion. I still use Acid Pro 4 for recording guitar and vocals, making drum tracks, and remixing songs (which it is excellent for).
Cakewalk is another good program. Not as easy as Acid Pro 4 (for me anyway), but still good and versatile.
I've heard many good things about FruityLoops, but never tried it.
None of those programs are free, but I believe there are trials for all of them if you want to try them out. Different programs will work well for different things though. Is there something in particular you're looking for? Can make a better recommendation that way.
Audacity is also a good program, and it's free. It's not as good as the pay programs, but it works well for a lot of people who just want to mess around. It's worth taking a look at.