I've been using the Internet as a gaming resource for 20 years now, and have delved around in a fair few places.
And the most useful by far to me has been... EN World
A Vibrant Community
First and foremost, EN World is a community, with the forums at its heart. The moderators and other users try to make the place a friendly welcoming atmosphere where you can talk about all aspects of your gaming.
Although originally focused on DnD, many of the forum users play (or have played) multiple systems and this is also reflected in the forums available.
Personally I've used the forums (as detomo) to find new players (in the real world), get help on story hooks, feedback on home-brewed content, try out a story hour, ask about rules issues and find inspiration for new adventures!
News from the RPG World
The front page has always had a constant stream of news, and this has broadened and intensified in recent years to cover pretty much all RPGs.
You can find details of the latest D&D sourcebooks, tabletop related Kickstarters, New RPG editions and homebrew content from around the web.
You can also find much more supported by EN World, including the ENNIES, which reward excellence in the RPG world every year, reviews on RPG products from many systems, and even their own products including three related RPGS, O.L.D., N.E.W. and N.O.W.!
Also check out the Perturbed Dragon cartoons if you have half an hour to spare....
So head over if you're not already a member and take a look around.