This is a topic that has been in pretty much every issue of Runners World since I started running back in the late 90's. I have found a few supplements that I am a firm believer in and I have incorporated them into my training routine. They work for me, but I can't say that they would work for everyone else.
Find what works for you (if anything) and be consistent about your use. You will see greater gains if you USE AS DIRECTED instead of using them whenever you feel like it.