The Oregon Knife Collector's Association
The Oregon club is one of the largest and most active in the country. Their newsletter is available online and is always full of interesting articles (though never about balisongs, for some reason). They also run the famous Oregon Show in April of every year. The site includes an calender of shows and events all over the United States. Check it out to see what's coming up in your area.
The American Knife and Tool Institute
The national industry organization for knife manufacturers.
Knife Rights, the national organization for knife owners and users.
Mr. Bernard Levine is one of the most respected experts on knives. His website includes a link to an article he wrote summarizing American knife laws by state in 1996. Much of that is still quite valid. This is an excellent resource. Mr. Lavine frequents knife shows. If you ever see him, say hi. He's a very nice man and always interesting to listen to.
Here's a great on-line resource for knife collectors. This is consolidated list of cutlery-related resources on the web, truly a "jumping off point" for knife collectors. As I type, this site has a dozen or so great articles of its own and links to over 650 other sites. It's sponsored by knife dealer Byron Rogers of Cutler's Cove. What he is offering here is not an extended advertisement for his business, but a great resource jam-packed with information. The site is well-organized and very through, a definite bookmark.
A very comprehensive collection of links for knife collectors. This site includes lists of knife makers, manufacturers, dealers, forums, and information sites such as balisongcollector.com. The concept here is that they've organized the site so well that (unlike balisongcollector.com) you can get to the link you need in just two clicks.
A.G. Russel Knives offers an extremely comprehensive "Encyclopedia" of cutlery terminology. This link takes you right to the encyclopedia page, but when you're done there, check out their home page for other nice articles including a nice guide to blade steels. Of course, don't forget to check out the knives they have for sale. A balisong or two shows up here from time to time.