Competitions, Records, and General Stats.

WCA - Official World Cube Association Website

Speedcubing - The Original Worldwide Records Page

Speedcubing Forums! 

Speedsolving - Largest Speedcubing Forum

Twisty Puzzles - Puzzle Builders/Collectors

WCA - Official World Cube Association Discussion

Yahoo - The Original Forum

Hardware:

Speedcubeshop - Cameron's awesome US-based store

Speedcube.se - Swedish-based puzzle shop