Here is a pretty complete O'Reilly library covering a wide range of topics in web development and networking. If you've never used any of these books before, check them out - they are very thorough, yet easy to follow.
Note: I am not 100% confident these materials should be freely available on this Ukrainian website that spells O´Reilly wrong in the URL. I will leave it up to you to either avoid the page or download the books quickly.
Update: Also check out the list of O'Reilly podcasts.
Update: Here is an even bigger collection.
Update: Here's another one. I think Diggers killed the site above, but I am leaving it there in case it comes back.
Update: Another library. Not O'Reilly, but quite good.