When Channel4 started off, a few guys who had made a rather comprehensive list of all the boards on 2ch, and were looking to have it hosted somewhere, in which we took the honors of doing so. The portal also contains a basic vocabulary, and links for more information.
View the 2ch Portal
As of now, the current list of boards is probably incomplete or inaccurate, as it hasn't been updated since 2006. Anyone with error corrections, additional links or anything else otherwise helpful, please just drop me a line.