There's the Game Explorer right here, along with lots of articles you can search for on specific openings. Click on "Learn" to find it and several other resources to help study openings with. You can also find lots of articles by using a search engine, just type in the name of the opening you want to look up.
www.365chess.com has a bigger DB than the Game Explorer here
www.chesscafe.com has lots of archives which inc many articles on various openings written by FMs, IMs and GMs
A book such as Fundamental Chess Openings might be helpful if you feel like splurging on a "general purpose" opening book. Fine's Ideas Behind The Chess Openings is antiquated as far as the theory in it goes but it might be worth looking into and you can get a used copy cheap in VG cond at amazon.
BTW I like thematic tnmts I've created several here and play in them from time to time but I'm not sure entering several at once is a good idea. Lemme know how it works out for you. GOOD LUCK!
http://www.amazon.com/FCO-Paul-Van-Der-Sterren/dp/1906454132
http://www.amazon.com/gp/offer-listing/0812917561/ref=sr
http://www.chess.com/blog/NimzoRoy/chess-opening-principles?_domain=old_blog_host&_parent=old_frontend_blog_view
I joined a bunch of Tournaments because I want to learn more openings. I hope that by playing them I learn about the variations. But I'll probably get more out of it when I read or watch videos about them as well.
Any tips to get most out of it? Do you know any online resources on one of the openings? Let me know! Thanks!