Have you ever used Yahoo groups to promote your blog or forum
 

Dear friends,
Yahoo groups is a hybrid email newsletter/forum group where members can share their photos, messages and links. You can make use of the forum feature by allowing members to post messages on the group forum or email out the messages. Members post messages to a specific group email address. You can start your own Yahoo group for your forum or blog or join another Yahoo group that serves your needs.

Yahoo Groups dates back to the early days of safelist marketing and they are still around. When promoting a blog or forum, any advertising method that spreads the word is fair game. Other places you might try include Google Groups, Facebook, Squidoo, Twitter and etc.

It's been along time since I have used yahoo groups for Seo work. They work o.k. back then but, there was an awful lot of spam.