John Robb mentioned Bletter in his blog today and said very nice things:
Bletter. E-mail newsletter demo. Looks very easy to use. It also creates an RSS feed. They are looking for beta users. This may be useful as part of the Weblog Network. It would also be nice if all you needed to do is put in your RSS feed and it would put the posts into the form itself. That way all you would need to do is work on the global template options.
I'm working on the RSS import into Bletter.