From the project's maintainer:

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VNC Manager is an easy to use remote administration tool which allows you to connect, 
view and take control of any computers running VNC or Windows Terminal Servers. It 
provides an easy to use intuitive GUI interface and unique features that can significantly 
improve the user productivity of network administrators. The list of features includes but 
is not limited to :

 - Latest RealVNC 4.0 and TightVNC 1.3 distributions are fully supported.
 - Thumbnail View allows multiple computers to be monitored on-screen at once.
 - VNC Manager has built-in support for HTTP and SOCKS5 proxies.
 - IP address and Windows domain/workgroup scan. Allows scan for active VNC servers.
 - Server Status scan. Checks from VNC server status. Can be started manually or set to update 
    server status via time interval.
 - VNC deployment wizard. Allows remote installation of TightVNC and RealVNC based servers.
 - External Tools. Allows to start an external application.
 - Can connect to Windows Terminal Server with a nicely integrated full featured built in viewer.
 - Start/Stop/Restart the remote Windows service.
 - Network administrator can reboot or shutdown remote computer.
 - "Reset Remote VNC Server Password" wizard. Allows you to mass reset password on a remote
    VNC servers.
 - Capture and save screenshot of remote VNC server screen.
 - VNC and RDP viewer window stretching.
 - Automatic search folders provide a quick filter for connected VNC and RDP sessions.
 - Send messages to other computers running Windows NT/2000/XP.
 - Default session. Allows to set default setting for newly registered servers.
 - Default password. You can specify a default password to connect with, or a specific one for 
    each connection.
 - Active sessions can be viewed in the separate windows or in Tab view panels.
 - VNC Manager does not require VNC Viewer to be installed. It uses an ActiveX VNC Viewer 
    control developed by SmartCode Solutions.
 - VNC Manager can send Wake-on-LAN "magic packet".

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It's Windows-only and not open-source. You can get it here:

     http://www.s-code.com