Easy Remote Desktop

It enables you to take control of remote computers with a single click from Mac OS X menu bar.
The app doesn't require to install 3rd party programs on the remote machine.

You'll have to simply turn on Screen Sharing in the Sharing pane of System Preferences.
It provides your favorite list of remote machines and the possibility to take snapshots of the remote screen and to transfer from and to the remote machine. The remote logins and passwords are securely saved by Mac OS X KeyChain service. In addition, it provides support for multiple simultaneous remote sessions.