If you are really savvy, you could probably just write a script to do this as well.. I remember writing a script to do something simliar at work.. it ended up blasting out 8000 individually addressed emails to every user in our mailsystem in a little under an hour..
You could look at 3rd party mailing list software... hmm.. free programs...most of the mailing list sotware that i know of are probably more than what you need and/or want. Most of them will require more setup that you probably want to go through.
You can try this.. Never tried it personally myself though