A few good reference sites I've found relating to kayaking:

PAN - The Paddler's Access Network (a local volunteer network dedicated to keeping river access open)

American Canoe Association (making the world a better place to paddle)

River and Trail Outfitters (great store by Harper's Ferry with knowledgeable, enthusiastic staff.  Where I bought my first kayak.)

Blue Heron kayak (a must visit site for wooden kayak builders)