I really don’t know how much can I recommend them since I have never used them, not because I have any ethical issues or something, its just that I find the links to be highly overpriced. Anyway you can still give a try to www.textlinkads.com and www.tnx.net (tnx=thanks).

I have also heard of http://www.textlinkbrokers.com/ and http://www.linkadage.com/ but have never used them.