I have already mentioned that I post on an online parenting forum and that is where I met Melanie from Graphicz Addicts. I am borrowing this from Heather's page, it is a good explanation of signatures. "For those of you who don't participate in message boards, often users have images that show up at the bottom of all their posts. It's called a signature and it's a way to make your posts more personal. When you use a signature it's easier for people to put a personality to a screenname which may be something like User135. Signatures can include text, pictures, links and animated images called 'blinkies'."
Mel makes custom signatures and blinkies. And I must say that they are pretty great. I have had Mel make some for me in the past. They really can help to make your signature stand out when you are posting on a big forum. Mel also has a blog so that you can stay up to date with all her great stuff.