Blogspreading is a free utility, which automatically appends a link to the latest post in your blog to your e-mail signature. This will easily catch the recipients’ interest and convert them to readers of your blog. Spread your blog around the world
The WiseStamp extension enables you to modify your email signatures
siggen is a cool email signature generator for encrypted ansi c (confused), brainf*ck, … signatures.
SignatureRandomizer – Select random signatures for your eMail application
SignatureQuote is a utility for anyone who uses electronic mail or posts to netnews or to an on-line bulletin board
Sigit is a customisable signature creator that can be run either as a daemon or as a normal foreground process.
MacSignify – Generates random email signatures