Reading and/or posting in this thread might help if you have Photoshop:

<a href="http://forums.eyesonff.com/showthread.php?t=71561">Photoshop Lessons and Sig Making Help</a>

If that fails, you can ask for someone to make you one in this thread:

<a href="http://forums.eyesonff.com/showthread.php?t=95602">Signature Service</a>