JMeld is a visual diff and merge tool. It is build to be fast with large files and runs on any operating system.
Development on sourceforge has stopped.
The project continues at github.
https://github.com/MrKuip/JMeld
XinDiff is a diff utility implementing WinDiff like GUI by an improved LCS algorithm. The key feature in addition to WinDiff is in-place comments for code review.