eSVNC, or "Easy VNC" is a relative newcomer, but is very popular due to its great featureset. It is based on TightVNC 1.2.2, supports file-transfers, Server-Side Scaling (SSS), and includes some great speed enhancements. You can find it here. It's available only for Windows and, except for the special features mentioned above, is fully compatable with RealVNC.

The eSVNC developer has recently transitioned his efforts over to UltraVNC. So it is unclear if eSVNC is still being actively developped.