There is a group buy going on right now at IK Multimedia on SampleTank Expansion libraries. You buy one library for $49.95 and you get SampleTank 2 XT and one extra library for free. Then as more people buy into the deal, you get more libraries for free. Right now it is up to four for one. I have Cinematik (movie-oriented strings and effects), Symphony Strings 2, Vocal Collection, and World Instruments. When there are 612 more users, it will go to five for one, and I will get either Hip Hop Instruments (even though I don’t do hip hop, there is some interesting stuff there) or Piano Collection 2.
This is all stuff I can play with my Roland-Ready Stratocaster. Right now I have it set up with an electric bass on the two lowest strings, horns on the middle three, and a cello on the first. Playing like this completely breaks down all the ruts that you get into as a guitar player, and generates new ideas for music. If I decide to record something, of course it is best to record the parts separately and layer them, but for jamming, writing, and fooling around, different instruments on different strings is great fun!
I have Kontakt 4, which is a much more powerful sampler than SampleTank, but new libraries for Kontakt tend to be very pricey. The target market there is people who are doing film scores, advertising, and hit singles, so it is pro, pro, pro and $500 a pop. This SampleTank deal has a lot of usable stuff for cheap, and I am going to have a lot of fun with it.
Here is a link to a quick jam I made with it: