WinMerge - WinMerge is an open source differencing and merging tool for Windows.
Modern CSV - A CSV editor/viewer
Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.
Rons CSV Editor - Rons CSV Editor / Now Rons Data Edit
Beyond Compare - Beyond Compare allows you to compare files and folders.
CSVpad - CSVpad is a handy free CSV (Comma-separated values) editor.