I just saw the signature of a Sharpfish at Indiegamer. It looks like this:
Latest Blog Post: New Year… Same Plans! || Reality Fakers – Fun Games For PC and MAC
Besides his website URL, the signature shows the latest Blog Post. I think that’s an excellent idea compared to show only “Game Blog”. If there’s PHP available in forum signatures then you can do this: make a small PHP script (or ask your friend) to fetch your latest blog entry and put it working.