You will get the most buyers on DP, but at wholesale prices. If you want to make more per link go elsewhere. By the way - I believe Sitepoint charges you to sell links, so keep that in mind.
ebay is a nice place, you can start a campaign for selling links! but then those are complicated things, perhaps selling links in the buy/sell section here is a lot better option,
ebay is the easiest place to sell links on. just get an eaby account, and buy some 1 cent ebooks to build some feedback. after you get 16 feedbacks you can start an auction in the Buy it Now category. take a look at some listings for links and make your own listing after that its a simple matter of answering questions and processing orders
IMO, you should negotiate with some buyer on a forum like DP. Instant payment, no middle man.. and its easy. You are in direct contact with the person!