2013 April Fools

PonyOS
http://www.ponyos.org/

Blizzard - Starcraft : Warhound is back
https://us.battle.net/sc2/en/blog/9369235

Atlassian - JIRA Jr
http://www.atlassian.com/jirajr/

Lambda The Ultimate - Migration to Facebook
http://lambda-the-ultimate.org/node/4709

Wolfram Alpha - Handwritten Knowledge Engine
http://blog.wolframalpha.com/2013/04/01/introducing-the-wolframalpha-handwritten-knowledge-engine/

DeviantArt - DeviantHEART
http://www.deviantart.com/deviantheart/

Twitter - Twttr
http://blog.twitter.com/2013/03/annncng-twttr.html

Google - Treasure Map
https://maps.google.com/?t=8

Google - Google Nose (BETA)
https://www.google.fr/intl/en/landing/nose/

Google - Google Blue
https://mail.google.com/mail/help/intl/en/promos/blue/index.html

Google - YouTube's ready to select a winner
http://www.youtube.com/watch?v=H542nLTTbu0

Google - Analytics reports visits from International Space Station
http://www.merocampus.com/blog/2013/04/01/merocampus-visited-from-international-space-station-google-april-fool-joke

Python - [Enhancement] Have all core library modules imported by default
http://bugs.python.org/issue17587

Stack Exchange - Chat with an expert
http://meta.stackoverflow.com/questions/174407/what-is-chat-with-an-expert

LDLC - LDLC BoX (French)
http://www.ldlc.com/n2497/LDLC+BoX/

OVH - Ethylcooling (French)
http://www.ovh.com/fr/all/a1036.ovh-derniere-innovation-ethylcooling