Ever need a temporary ad-hoc mailing list? Check out conversate. It goes beyond simply emailing a list of folks, generating a web archive of your discussion and an RSS feed you can subscribe to or link folks to. You can open it to participants beyond the initial group easily, and it has a handy browser bookmarklet. It's really more of a hybrid - depending on how you configure your preferences, this could be used as web-based discussion tool or you can conduct the conversation solely through your email client. At any rate it's free and has a clean easy-to-use interface.