BOX Creative, LLC

1. Random Signature

By default, Random Signature will pull quotes from a BrainyQuote RSS feed, but you can replace this with a file of your own. If you’re comfortable in a text editor, an easy way to generate your own feed is to use the default RSS file as a template and edit it to taste for your own needs.

2. Wisestamp

You can also pull in items from an RSS feed right into your signature, making it a great way to promote your latest blog post, Flickr () photos, status updates, random quote, or pretty much anything you can stick into an RSS file. For a walkthrough of the Wisestamp featureset, check out the tour video below.

3. Location in signature

Frequent travelers and virtual office workers in distributed teams will especially enjoy this one. Another Gmail Labs feature, Location in Signature does just what it says: appends your current location to your outgoing emails.

4. Black Canvas Gmail Signatures

Another Firefox extension, Black Canvas handles both HTML signatures and managing multiple sigs for different email addresses automatically. You can also set up to four different signatures for each address and switch between them as well.

5. Signature Tweaks

This add-on is less about editing your actual sig and instead is about modifying where it is positioned by default. Normally when you use Gmail’s “Reply” feature, your signature gets appended at the very bottom of the email, after the quoted text you’re replying to. This isn’t always the desired behavior, and many folks would rather have their signatures be included after their reply text and before the quoted text. Read more at mashable.com