The actual layout is just normal HTML design, albeit with a few pertinent points. You can find a good article about the creation of HTML newsletters over at
http://www.sitepoint.com/article/cod...il-newsletters
As for sending the e-mails - that was a LOT more complicated. In the end I settled for a program called
First Mass Mailer. Its not as well featured or pretty as many mass mailers, but it does its job and accepts raw HTML input. If you have real money to flash around, the
Hope Mailer looks utterly divine and works a dream... but is quite costly unless you intend to send lots of newsletters with a commercial aim in mind.