I just finished tweaking a WordPress plugin I'd created for myself that adds a signature file to the end of any emails that WordPress sends out (eg. comment notifications generated by other plugins...), and now it's available for free download (you'll find it in the "WordPress" section -- sign up for free if you don't have an account).
MailSig has the following features:
- Create an unlimited number of signatures (put each in a text or PHP file, and upload it to the plugin's "signatures" subdirectory).
- Select which one to use from a dropdown list in the plugin's configuration panel.
- PHP signature files can generate your signature dynamically. For example, if you want your signature to contain information about a sale during only during a specific time period, you can do that with PHP code. Once the time period has ended, your code can automatically switch to a different signature.
Any features you'd like to see added?