What alternatives to VNC are there for Linux?
Solution 1:
If you have a reasonable fast link, X11 is the native remote technology on Linux and every other Unix-type system, as the X11 system was designed from the ground up to work over the network. These days, it's mostly used with ssh port forwarding (like ssh [email protected] -X), and NX, mentioned in the answer by alvosu, "merely" improves on the compression, making it accessible over slow links with a high latency.
Solution 2:
NX technology is a computer program that handles remote X Window System connections, and attempts to greatly improve on the performance of the native X display protocol to the point that it can be usable over a slow link such as a dial-up modem. FreeNX - Free Software (GPL) Implementation of the NX Server.
Solution 3:
Depends why you need it. xrdp is a wrapper around vnc but it solves most of the difficulties I have with vnc on Linux. http://xrdp.sourceforge.net/
Solution 4:
And if the box you are connecting to virtualized using KVM (or RHEV), you can use Spice which performs exceptionally well.
http://spice-space.org
Solution 5:
X2Go is a software that enables you to access graphical desktop of a Linux computer. It performs really well even over low bandwidth connections. You can choose to use an entire desktop, or have only a single application (over X11 with a persistent session). If you are familiar with solutions like GNU Screen or tmux for command line sessions, X2Go is a similar tool for graphical sessions. X2Go uses NX technology under the hood.