All these resources will help you learn more about cubing and how to get faster.
The SpeedSolving Forum is a great community where you can ask questions, compete online, and get the latest news and dicussion.
CubeSkills.com is where Feliks Zemdegs himself teaches you how to learn and get fast at 3×3, 4×4, 5×5, OH and Megaminx. All for free!
SpeedSolving Wiki has info on methods and useful algs although some of the info is outdated.
World Cube Association is the website where all official competitions are hosted.