Web 2.0 Properties?

I have started building a bunch of web 2.0 sites, like one on live, vox etc.. I see alot of people use this to strengthen there main sites. So my question is whats a good strategy to link with these.

If I have 20 2.0 sites, and start posting in each one 3-4times a week is it best to link to different pages of my main site or should I wheel them together sometimes, sometimes dont put any links and with the rest of the time link to my main site?

Or is there a better way?
Thanks

Also each time I write in these I ping the updates