A must read for all practicing jazz musicians is www.jazzstandards.com. It has information on 1000 most frequently recorded jazz standards as well as detailed analytical and historical notes on the top ranked 100 compositions. Looking for a particular piece for example will give you information such as the historical background, musical analysis, musicians comments as well as CD recommendations. This is a highly recommendable site, especially if you are learning a new tune and need relevant information quickly. The suggestions of famous recordings I found particularly useful, as this is often the most time consuming part when looking for information on a piece you haven't played before.