These are the sites I've been visiting for years gathering audio knowledge. Just a bit of advice, forums are a great place to get answers, but it's always a good idea to start with a search and see if anyone else already solved your problem. Also, use caution if and when you do post. There's nothing like getting started only to find yourself the subject of a flame war for disregarding the rules or for no reason at all, just because some troll needed someone to take shots at.

Another great source of info is manufacturer websites. Way back in the infancy of the web I learned a great deal from just the few manufacturers that had sites up at the time. The menu now days is awesome. Reading those sites is a good way to learn to see past the hype and figure out what really matters in terms of gear. Now, on to the links

  • ProSoundWeb is an awesome collection of blog posts, articles, links, manufacturer and venue announcements, and there's also a really deep forum but beware, some of the best minds in the biz hang out there, and also some of the toughest trolls. It's also more or less a digital version of a print mag.
  • FOH Online is another onlie version of a print mag. The page is updated fairly frequently but the really good articles show up once a month. A nice feature is the reader at the bottom of the page where you can peruse the material as it appears in the print version. There are also Android and iOS apps.
  • Pro Audio Space has a great collection of blogs, articles and other info. They also enforce Rule #1: Don't Piss Off The Sound Guy!
  • Control Booth is a set of forums aimed at theatre people, high schoolers in particular. The content is miles deep and relatively free from trolls. A lot of pros hang out there as well and serve to temper some of the ill considered advice given by enthusiastic high school kids. 
  • Gear Slutz is probably the premier forum for audio on the web. Over a million threads with dogs big and little hanging out swapping info. Even the manufacturers hang out there. 
  • r/audioengineering is a sub on Reddit where the gentlemen of the internet hang out and discuss all aspects of audio from stage to studio, bedroom to stadium. Troll Free Zone.
  • r/livesound is a sub on Reddit dedicated to live sound. Another spot where heated arguments might break out but the tone never degenerated into yo mama insults. Troll Free Zone
  • AAPLS or is a usenet group dedicated to serious live sound. It's pretty much awash in spam posts and the trolls that hang there are legendary. I've learned a lot there over the last decade or so and it's worth a look when you've got some time to kill. (Think twice about posting a question... then don't do it.) 
  •  Pensado's Place is an ever growing collection of interviews with the heaviest of heavy hitters in the record business. Engineers, producers and so much more. He takes questions from viewers and every week takes you "Into The Lair" for a little one on one studio time.
  • Rane Notes is a collection of white papers that an equipment manufacturer keeps up on their site. It's a great place to start if you're looking to learn the basics and there might even be a few tidbits for the old hands as well.
  • Instructables is the site for the DIY crowd. There is simply some phenomenal work being done out there and some of it is really well documented here. Not the greatest place to learn the fundamentals but if you're of a mind to tinker or even just think about it to sharpen the mental skills it's the tops. I only look on weekends because I'm prone to browse for hours. Also one of the hot spots for Arduino developers, check it out!
  • Mouser is a supplier of electronic components that is pretty much unbeatable for the depth of their catalog. If you're looking for an obscure replacement part, if you're willing to dig you can likely find it here.
  • Audio NowCast is a pretty deep collection of audio podcasts covering a pretty wide range of topics. The archives go back for years. I like to have a couple on my iPod for my commute, or fire one up on the lappy during lunch.
  • Microphone University is a section of the DPA Microphones website that does into pretty good detail about micing techniques, especially stereo and other multi-channel setups.
  • The Lefsetz Letter is a truly thought provoking item every time it comes out. You can subscribe by email or browse the archives.