The Duckworks Magazine is just one of the greatest sites you can visit. Owned by Chuck and Sandra Leinweber who are great people to work with--and based in Harper, Texas. Chock full of great articles and information about a huge variety of boats. You can find some excellent designs here. There are several really good designers that post articles as well. One of my favorite sites. Try it--you'll like it!
The Kayak Forum sponsered by Guillemot Kayaks which is owned by Nick Schade is the grand daddy of all kayak forums. Not sure they've how long it's been in existence but I found it many years ago. Great source of information.
As with all forums, use common sense when reading the recommentdations and advice by some people.