Diablo III Armory Page
The Diablo III Armory is a Battlenet byproduct hosted directly by Blizzard Entertainment. It allows anyone to browse through Sanctuary, casually looking through the skillsets, equipment, and current progress of every single character in the game. A link can be found here:
Apparently, the Armory does not have it's own home page, you must go to a player's page directly. The Search function in the top right can be used to search by battletag or character name to find the player you are searching for.
In addition to this, DiabloProgress pulls from the same API and allows further comparison as to how your character and gear stands up to pretty much everybody else in the world, though DP only displays characters over level 55, at this time. A link can be found here: