Beyond Compare - Beyond Compare allows you to compare files and folders.
SISTRIX - SISTRIX toolbox is an SEO tool for professionals helping reputable companies to constantly improve their websites.
WinMerge - WinMerge is an open source differencing and merging tool for Windows.
Page Weight - Find and fix heavy images on your website
Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.
PageSpeed Ninja - One-click page speed boost for WordPress