I see a lot of trends in magazines and mail order catalogues; to check out those that look interesting I'll go to Amazon.com to find books on that, read the reviews for an idea, and then I'll go to my local library and check out those books by interlibrary loan. That way I get to REALLY check out the trend without spending ANY money on books first ... and being disappointed later ... and being stuck with a book I paid too much for to get any use out of. At $23 to $28 a pop, quilting books aren't cheap.
I also check out
http://www.allpeoplequilt.com/ - GREAT resource for what's happening in terms of technique and gadget trends.