autopen :

Autopen is a google-chrome extension allowing you to create html email signatures for gmail/google apps.  It has a full rich text editor that makes creating html signatures easy but still allows you to drop into the html source for more power. Create as many signatures as you want and associate them with from addresses to set up multiple defaults.

New Features:
*Synchronize your signatures with unlimited computers.
*Updated editor interface to create sync accounts.
*Manual overrides for sychronization issues.
*Fixed editor double space issue.
*Updated core libraries and made optimizations.

Features:
*Unlimited Signatures
*Insert Signatures before/after replies/forwards
*Full rich text editor makes creating html signatures easy and fun
*HTML source view for signatures lets you take your signature look to the next level
*Set default signature for multiple from email addresses
*Quick Signature Insert - allows you to remove or change/insert signatures
*New editor Interface for small Screens
*New full featured rich text editor(with source view for those who want to edit the html)
*Updates all screens with gmail/apps when you make a change to signatures
*Editor opens in its own tab
*Set/Change names to your signatures so that they are easy to find
*Disable any default inserts either for an address or for the master default
*The editor is open from the Autopen icon(in the gmail/apps interface) or the extensions options button