From Unify Community Wiki
- Unity Awards - Honoring the best content made in Unity each year.
-  - Flight Simulator Contest April 1-30, 2013 at 3dcognition.com.
- GEE Unity Game Contest - Contest runs until 29 Feb 2011. Create a multiplayer game with Photon's Unity3D plugin, and publish to the Wooglie games portal. Prizes include: Unity Pro license, and 1 year of Photon Cloud hosting. View Thread Here
- UniKnowledge - Contest runs until October 1st, 2009. Create short form tutorials and simple example projects with good documentation and win some amazing prizes!
- Unity Explosivo! - A for-fun Unity user contest to create the coolest & most imaginative explosion in a fixed amount of time. Contest runs for 3 weeks from Saturday June 23rd, 2007 @ Midnight until July 14th 2007 @ 23:59h. More details inside...!
- UniKnowledge 2 - Contest runs till sometime, 2010. Create short form tutorials and simple example projects with good documentation and wind some amazing prizes. This is the second contest of a hopefully long running set of contests.