The horribly named, Why Your E-Newsletter Doesn't Deliver Like You Hoped actually offers a pretty good checklist of things your e-newsletter should include.

I think we're just about ready to launch a couple of new newsletters (our first venture into the realm of e-mail). If you are an employer/hiring manager, or if you have a job - particularly a clerical or accounting job, then you should think about Subscribing (depending on when you click by, it may still need a few coats of paint, so please don't mind the mess - it works even if it looks like crap).