Nice tips Banzai. You're definately right about ripping beats/drums/samples/loops etc from CD, I've found that is an easy way to create new stuff and if done properly sounds completely original. The main problem has been varying levels and pans on different samples. These can be easily sorted though by compression or pan manipulation. Apparently, the best way to pan a virtual kit is this:
Bass drum-central
High hat-slightly left
crash-way left
snare-slightly right
Toms-central
Ride-way right
I guess it just replicates the way a real kit is setup but it just gives a broader projection of sound and sounds live and professional. There's loadsa different ways to do this though.
Peas. (and carrots)