I don't have anything to add to the incredible and huge list already mentioned here in terms of recordings. There is a book that I've read awhile back, however, that has helped me understand and enjoy jazz immensely and it might be worthwhile for those who are new to check it out. The book is Jonny King's "An Insider's Guide to Understanding and Listening to Jazz." King's knowledge and prose combined with his enthusiasm make for a quick and entertaining read. Higly recommended.