MailChimp presents 4 free HTML e-mail templates that are well-optimized for most of the e-mail applications.

Templates include a basic newsletter, postcard and 2-column designs.

Free E-mail Templates

You can also find newsletter coding tips at the same address and a free e-mail marketing e-book which covers email marketing benchmarks (average open/click rates, bounces, unsubs), how spam filters work & more.