The Internet is a crazy place sometimes. You can literally find anything you want. This, project lets all you laptop DJs play around with mixing a variety of samples together. Might be just the thing to whet your appetite and encourage you to get into making music for real.
The basic premise is this. Someone laid together a ton of youtube videos on one page, each containing a short instrumental riff. You start/stop them as you want (you can play them all together, even) and somehow it just works. You can see if their FAQ answers your questions.