Ok, I now have a few sites about the same niche. I am wondering how should I go to put links on each of these sites , linking back to the others ? Wouldnt google penalize in some sort of way ?
just link from pinpoint relevant pages to pinpoint relevant pages for best effect. Only link one way. See if you can chain the sites together so that sites higher in the chain link to sites down the chain but not up the chain. Don't even think about linking from homepages or site wide. Make the links from within the body of text.