TightVNC is an enhanced version of VNC which includes a lot of new features, improvements, optimizations and bugfixes over the original VNC version. TightVNC is absolutely free, cross-platform and compatible with the standard VNC.
Just like the original VNC, TightVNC can be used to perform remote administration tasks in Windows, Unix and mixed network environments. It can be very helpful in distance learning and remote customer support.
For more details, follow the above link.
New features in TightVNC development version
Check out the screenshots: http://www.tightvnc.com/screenshots.html. They've added things like a better viewer, file transfer, ability to share individual windows, and so on.