WinMerge - WinMerge is an open source differencing and merging tool for Windows.
AptDiff - AptDiff is a visual text / binary files comparison and merging utility for Windows.
Compare - Download Notepad++ Compare plugin for free. Comparison plugin for Notepad++ editor. Comparison plugin for Notepad++ editor.
WinDiff - Download Windiff : free files and folders comparison tool
TableTextCompare - Compare 2 tab-delimited or comma-delimited (csv) files, creates a diff report
Online Text Compare - Online Text Compare tool allows you to compare two documents in different formats.