I picked up Ed Friedland, Josquin des Pres and Stephen Richter through Amazon and ripped the CDs in iTunes.
I use a couple of different programs for music composition that use mp3, wav and aiff files, which iTunes keeps organized.
Now that I have the spare iPhone, having all my audio files in one library, on one device, makes it easy to search for a particular style of beat.
The repeat function in iTunes is a big help, because I can loop any of the samples for practice.
Yes, I am aware that iPhone 4 is coming out, which is why they are having a fire sale on the 3Gs. I have already updated my 3G and 3Gs to iOS 4.