kdiff3
Beyond Compare
WinMerge
Meld
Araxis Merge
DiffMerge
P4Merge
Devart Code Compare
Cr4yon
Ryeboard
Scribble Online Whiteboard
Whiteboard Team
IDroo
OpenBoard
Stormboard
Conceptboard
kdiff3
Cr4yonBeyond Compare - Beyond Compare allows you to compare files and folders.
Ryeboard - A practical and visual workspace for modern teams
WinMerge - WinMerge is an open source differencing and merging tool for Windows.
Scribble Online Whiteboard - Scribble Online Whiteboard is an advanced collaborative whiteboard solution that allows you to draw the sketch using the web-based or mobile platforms such as iPad/iPhone and Android.
Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.
Whiteboard Team - Work visually, together!