Emails based on user activity
 

A first approach would be to include profile field (user field information) and past forum activity and then send emails either on specific time frames or on special times (when user gots promoted, posts first post). Imagine a vbulletin.com birthday mail from Ray:
Quote:
Originally Posted by Ray Morgan
Hey username,

Happy Birthday! I wish you all the best for your new year. I hope everything turned out great with your new server and that George could help you out with his server management advices. (activity in server configuration forum)

I thank you for your bugreports on the new blog, they were very helpful. We were happy to solve most of them. (activity on bug reports)

Did I forget to say thanks for your latest entry in the vbulletin How TO? Our users seem to love your how to. (you posted a approved thread on the vbulletin how to that got high rated)

With you a great day!
Ray Morgan

You see there is extreme potential for these kind of things without even producing another cms / project tools / blog and not even change anything in database structure. It's about selecting the right data, combining it and present it to the user - as a user guide (go to these forums, they have posts you'll be interested in) up to emails like shown here.