The trick to get a link bank from others is to send them an email "personally". I have been successfully getting link back by writing email personally to blog/ site owner explaining why a link back will benefits both parties. Why should one give you a link back when they are already PR6 and your are just PR123. Formulate your email by putting you in their shoes. I did this few times a month targetting quality site only. Too many times I see people sending out bulk email hoping to get an link back, it just doesn't work. For those who hate G, try www.cuil.com
If you know your niche, you should know similar sites. Create a links page with their sites and ask for the same. I am tired of folks wanting to link cut-n-paste credit sites!
Even if Google slaps your PR or your SERPs for selling links, you can always get rid of them and get back into the system. Most of our sites will never warrant a manual review by G so you might as well be avant garde and try out all the theoretically "evil" things like selling liks, posts and various other options because just cuz Google says it's bad doesn't really mean it is.