Emailology - The Science of Looking Good in the Inbox. While catching up on some rss feeds today this little gem popped into my window. It contains a boilerplate for HTML emails in loads of email programs. The compressed mode which is 109 lines of code.
The site also contains faq about common email clients for individual styling or tips. You can also view a standards guide to see which tag and attributes are supported to get the most out of your campaign.
This site is definitely one that will be in my links list. I can see this coming in very handy when I'm doing my next client mailer.