dark.codes

You may put in pretty much anything (including 32bit IDs). For example:

• http://steamcommunity.com/profiles/76561197978046717
• 76561197978046717
• 17780989
• http://steamcommunity.com/id/the_monkey/
• the_monkey
• STEAM_0:1:8890494
• 1:8890494

or any variation therein.