So, I am looking for some google optimization. I have a service that sets up wordpress blogs for people. I currently have several hundred blogs running around out there and I would like to optimize them for google and bump up their search rating but I am out of ideas.

Sitemaps, robots.txt files, no 404's, compression enabled etc. What I would like to do is set up a mysql database of URLS for each of the blogs and insert a line of php that pulls from that database and places a backlink at the bottom of every blog for every other blog.

So i want to know that do you think this is a bad idea? And do you have any other suggestions for what I could do to raise my entire network of blogs up on google?

Thanks !