Mingle Forum Guest Info allows you to enable guest posts to Mingle Forum without registration while still collecting contributor's email info.
Mingle Forum is the best WordPress plugin forum. This add-on plugin makes it easier to run a forum with guest posts without requiring registrations. Guests are required to add a name and email. This feature is especially useful for support forums. The guests don't have the hassle of the registration process, yet can get direct responses with their email. In addition, instead of a bunch of anonymous Guest posts, there will be names and avatars. Guests can subscribe to replies, too. If you have the "Ban Hammer" plugin installed, it will be automatically used to filter spam email addresses.
You can try Mingle Forum with the Guest Info add-on at my site: WPWeaver.info