I think it's called a Blog-Role.
Basically, one of the things that drives blogs is that they all inter-link. This linking is how they get discovered, and read, and it is based on a system of reciprication. The linking helps the blog, but it will also really help the forum, since each member will actually be tracking down and acquiring links to your forum.
Essentially, it's like a post that let's them input a url and url-name which is then put on a sidebar automatically.
For example:
http://tutakai.typepad.com/tutakai/ - the right-hand collumn
http://poliblogger.com/ - right-hand collumn
http://www.redlinerants.com/ - right-hand collumn.
Thanks!
jEd