Cool sites about Rubik's Cube
Solution Pages
Kantenkreuz.de by Jürgen Fischbach is a well designed solution page for the Rubik's Cube.
El ocho tumbado by Javier Santos provides a solution guide to the Rubik's Cube in Spanish.
Rubik's Zauberwürfel by Markus Pirzer. The first complete interactive solution for the 5x5x5 Professor Cube.
Speed Solving
Speedcubing.com is a first class news feed for cube related topics. The site also holds a list of (un)official cube records, of which some are really crazy.
Dan's Cube Station by Dan Harris is dedicated to speed cubing. The site hosts the famous weekly Fewest Move Challenge as well as a gallery of speed cubers and lots more.
Gilles and his Cubes by Gilles Roux provides very creative and funny videos showing all the other things one can do with a cube besides scrambling and solving it.
Planet Puzzle by Katsuyuki Konishi is a beautiful and very comprehensive site about Rubik's Cube.
Software
CubeExplorer by Herbert Kociemba features extremely sophisticated solvers for Rubik's Cube. The solver used in my own CubeTwister program is derived from an earlier version of his program.
Twisty Puzzles
Jaap's Puzzle Page features an awesome overview of cube like puzzles. Lots of them can be played online using a JavaScript enabled browser. The site also contains an excellent documentation about the mathematical aspects of the cube.
Sticker Shops
Olivér Nagy's Sticker Shop offers sticker sets in excellent quality for many of the Virtual Cubes and replacement stickers for twisty puzzles (site language: English, Hungarian).
www.StickersShop.net is producing printed sticker sets for many Virtual Cubes designs along with quality stickers for twisty puzzles (site language: Russian).