Wikipedia
Remmina
Remmina is a remote desktop software client for Linux-based computer operating systems. It supports the RDP, VNC, NX, XDMCP, SPICE, XDMCP, Nomachine nx and SSH protocols.
Remmina is in the package repositories for Debian versions 6 (Squeeze) and later and for Ubuntu versions since 10.04 (Lucid Lynx). As of 11.04 (Natty Narwhal), it replaced tsclient as Ubuntu's default remote desktop client.
Remmina, written in C, is a front-end of FreeRDP, a fork of rdesktop aiming at modularizing the code, addressing various issues, and implementing new features.
Remmina is available in three different packages; GTK+ application, GNOME application and the xfce panel plug-in.