I'll use this thread to help compile up stuff that can help out new players to DoTA 2. Whoever gives a new tip or link I'll be sure to credit them.
Now let's start off with the basics:
DotA 2 wiki: http://dota2.gamepedia.com/Dota_2_Wiki
This will be the main site where information about stuff in the game will be constantly added. Some good stuff even includes all the voices for each hero and announcer packs.
DOTAFire DotA 2 Builds & Guides for Hero Strategy: http://www.dotafire.com/
This is one of the main sites to look up builds and guides for each hero. A word of warning though that some of the guides may be a bit outdated, but it's still a good place to get information.
DotA 2 Reddit: http://www.reddit.com/r/DotA2/
Like the LoL reddit section, it's a nice catch-all section for anything DotA 2 related. Mostly involves funny/cool stuff, as well as daily discussions about an in-game item or hero.
Now onto helpful Youtube channels:
This guy posts up entire games of a hero he picks, so you can watch his videos to get an idea of how to play just about any hero. Just type up "Purge plays" and whatever hero you want to learn, and he'll have a video of it where he either does a live commentary on his gameplay or does a replay commentary.
Usually his replays has him able to point out more mistakes since he's not so engaged that he can see where he goofs up.
This guy was a really pro DotA player, where he was famously known for playing Zeus. He does a mailbag series where he does a presentation style video of tips and tricks for the game. Examples are how to still win when you're behind in a game.
This is a mega-channel with videos of all types. Most helpful for new players would be the introduction videos they make for each hero. There are occasionally guides or the heroes as well. Just search up "DotaCinema" and whatever hero you're looking for and get a intro video to that hero.
Other videos series of notice are:
-Learn DotA 2
-Top 10 Weekly
-Fails of the Week
-DotA 2 Mythbusters
-DotA 2 Symphony of Skills
-DotA 2 workshop items
While not entirely a helpful channel, this person deserves notice:
Pyrion Flax: http://www.youtube.com/user/tedhimself
For humor, there's the famous Pyrion Flax, who makes satirical videos on how he plays DotA, include "guides" to heroes. He also got his own announcer pack into the game (think the LoL announcer voice that tells you when someone gets killed, but way more expansive and interactive).