http://htmlemailboilerplate.com/
There are various new and exciting stuff with the website development like HTML5 and CSS3.
But, when it comes to designing HTML e-mails, it is still the tables and hacks for improving compatibility with different e-mail clients.
HTML E-mail Boilerplate is a project which presents a starting point for HTML e-mail design and includes solutions for the major rendering problems with the most common email clients.
The code is very well documented and the download pack includes a non-documented version).
