Robomongo – cross-platform MongoDB GUI client.
Update: Mac OS X and Linux(as Debian/Ubuntu, RHEL/CentOS packages) versions released.
Update: Robomongo officially changed it’s name and released two different products Studio 3T and Robo 3T. Old robomongo is now called Robo 3T. Studio is for professionals.
Update: from October 2022 Robo 3T is named Studio 3T Free.