There are roughly a bajillion League of Legends fansites and blogs out there, so this article will focus on the main resources you can tap. A complete list of all League fansites would cover over a dozen articles; I will try to cover other useful sources of knowledge in future editions of the Guidebook, though.
Official League of Legends website -- If you've never been here, you probably don't play League of Legends. The official website is your gateway to champion information, sneak peeks of new features, streams of pro players, patch notes, and other information. You'll also need to go here to download the game. A lot of the links here are displayed in the game client, which will pop open a web browser if you click on one of the news posts there.
League of Legends forums -- The best place for information about League of Legends is the official boards, although specific information is somewhat hard to find. If you've exhausted all your other resources, you can probably find what you're looking for here. However, be advised that the forum attitude is somewhat harsh, as one might expect from a competitive game. I would advise looking elsewhere for most of your information unless you're thick-skinned.
The Tribunal -- Although it's a part of the main LoL website, I feel that the Tribunal deserves special mention. If you've reached the level cap of 30, you can participate in a player-run voting system that punishes unsportsmanlike conduct. Offenders are put before a player jury, and the jury votes on whether the player should be convicted or not. If you make it to level 30, I highly recommend participating to remove the worst elements of the League community.
League of Legends Wiki -- Although it loses a lot of marks in my book for being hosted on Wikia (and thus has annoying ads), the LoL Wiki is one of the most detailed wikis I've ever read for a video game. It is regularly and rapidly updated with information; any time a dev hints on the forums that something might change, relevant parts of the wiki are updated minutes later. News and patch notes are uploaded to the wiki at a blinding speed. If you want specific numbers on a particular item, ability, or game feature, there is really no better place than the wiki.
MOBAfire -- MOBAfire is one of the best sites for champion-specific strategies. If you're looking to pick up a new character or improve gameplay on one of your old standbys, this is the first place I'd recommend. MOBAfire also hosts tournaments, has links to top player streams, and has tools to let you create your own strategies and host them.
Team Solo Mid -- While MOBAfire is one of the best sites for advice from other players, SoloMid.net is probably the best place to get advice from pros. TSM is one of the best League pro teams in the world, and its members have some of the best guides on the Internet. If you're an expert and trying to squeeze out maximum performance from your character, SoloMid is one of the best resources.
LeagueCraft -- Another great community resource, LeagueCraft provides very similar services to MOBAfire. Some people prefer this site to MOBAfire, and both sites are great. If you're looking for guides for a particular champion, you should stop here as well.
Counter Logic Gaming -- CLG is considered by many to be the top American pro team, and like TSM, it boasts a wonderful website resource for players. Instead of being a huge archive of champion guides, clgaming.net is a huge pool of opinion articles and editorials about League of Legends. It features Elementz and his popular tier lists as well as Stonewall008's jungle tier lists. However, those aren't the only features on the website, and all of the information is excellent.
League Replays -- Because League of Legends does not currently feature replays, LoLReplay is probably the best third-party addon for League of Legends ever developed. You can watch replays of top players (as long as you know their display names) or just study your own. This is an essential tool to improve your game, and I will be referencing it a lot in future articles. It's a must-download!
League Statistics -- There are several websites that datamine the game, but lolstatistics is one of the more prevalent. It's a repository of datamined information, which can be useful in theorycrafting. It's not very useful to most players, but it does feature a lot of interesting trivia.
Dominate Dominion -- Not many websites sport detailed information about the Dominion gametype. DD is a website focused exclusively on the Crystal Scar and how to capture and hold more points than the enemy. If you're looking for Dominion strategies, this are currently the best source available. It also has links to the various semi-pro Dominion teams (there is no Dominion pro scene yet, although there are pro-caliber players), which is great if you're looking for players to download replays for.
Riot Games' YouTube channel -- Riot puts out regular videos on its YouTube channel. These include community spotlights on art, music, and other media related to League of Legends as well as the somewhat infamous Champion Spotlights, which give helpful info related to the various heroes in the game. While Champion Spotlights aren't always the best guides on how to play a particular character, they do provide a lot of useful info and are a great starting point. Lastly, you can subscribe to the channel and get a free Unchained Alistar skin as well as unlock Alistar for free. Watching cool videos and unlocking a free character sounds pretty win-win to me!
League of Legends' Facebook -- If you're a new League player, you should check this out. It rarely has any information that you can't get on the LoL homepage, but it does offer a free Riot Girl Tristana skin if you Like the page. It also unlocks Tristana for free! While unlocking Alistar from the YouTube channel is pretty cool, Tristana is one of the most bread-and-butter ranged carries in the game, so getting her for free is amazing.
We understand what it's like to climb the skill ladder in League of Legends. The Summoner's Guidebook teaches you the tools you need to get a competitive edge. Whether you're climbing the ranked ladder, playing Draft Dominion, or getting crushed by intermediate bots, every enemy has a weakness. And every Thursday, Patrick Mackey shows how you can improve improve on yours.