The importance of using email signatures is generally well accepted today. A signature should include, at minimum, your name, company name, contact information (not including street address) and company branding statement but can include so much more. With all of the options today for signatures, you want to make sure that you don't "overdo" such that people cannot hear your email content because the banner is so large, or loud, that it is taking over the screen. Keep it simple, small and information packed !
One feature available today that we feel is well worth the addition to your signature is inserting an RSS Feed from your blog. The feed will automatically update your email signature with a link to your most recent blog post. This will absolutely drive traffic to your blog as long as the content is relevant to your customers receiving your emails.
RSS Feeds added to your dynamic signature are another way to get your blog content in front of the largest possible audience but will also work with any web content. You can choose to drive the traffic to your latest web page content or use the same functionality to insert your most recent newsletter link provided the newsletter is located on the web.
Here is a shareware, freeware and trial ware list of programs that can help you manage your dynamic signatures.