We've never had very good luck with affiliates. However, if you have a high traffic page or link, there's no reason not to try adding affiliate links to those pages. Typically you will earn 6-10% commission on any sales that come through those links. Remember, however - if you add affiliate links and don't have any unique content (descriptions, reviews), there is no way that Google will send you traffic - they'll consider it just a crass affiliate page, with no redeeming content of its own.
