For the best selection of AN adapters, fittings and hose, check out Earl's:

I wouldn't be racing with any confidence if I didn't have all the books of one of the all-time Legends of automobile racing, Carroll Smith:

The Formula Ford Underground was a great source of information for all racers, though it's now only an archive of information:

 

Since the demise of the FFU, two websites have cought my attention as great resources. Formula1600.com is strictly a member forum for sharing information, getting information as well as buying and selling cars and parts. This site is laid out in a similar manner to FFU but the forums are broken down into more precise topics.