Valve's Summer Mapping Initiative, an officially sanctioned outlet for the Portal 2 community's creativity, has come to a close. The winners -- Patent Pending (pictured above), Infinifling, and Edifice -- are available to download and play for free, in addition to a bunch of runners-up.
While we're waiting for the Valve-made downloadable content that's due out later this summer, I suggest giving the full list a perusal. Those looking for more of a challenge from Portal 2, especially, will want to try some of these out.
Valve picks new Portal 2 PC maps [Eurogamer]
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Instructions on how to play the maps, courtesy of the handsome and lovely people at Valve:
1) Download the map file from ThinkingWithPortals.com.
2) Open up the .ZIP file after it has downloaded.
3) Find the location of your Portal 2 installation on Steam. This is most typically found under:
Windows PC users: C:\Program Files\Valve\Steam\steamapps\common\portal 2\maps.
Mac users: ~/Library/Application Support/Steam/SteamApps/common/Portal 2/portal2/maps
Note that your installation location may vary, depending on your initial install directory.
4) Copy the .BSP file located in the downloaded file to the directory above.
5) Start Portal 2
6) In the game's main menu, select "Options->Keyboard and Mouse"
7) Set Allow Developer Console to Enabled
8) Press the tilde (~) key to access the console
9) Type map "mapname here"
10) Solve the puzzle!