Greetings:

MajorDomo is by far one of the best listserves out there, but may be a bit on the geeky side.

Why not check out Mailman. It's GNU and has more webbased administration, so it might be of use to you:
http://www.gnu.org/software/mailman/

It's used by a lot of HUGE sites, so you know it's scalable and secure.

You could probably get your host to install it for you if you ask really really nice.