F-Droid - F-Droid is an interesting alternative for Android users who want to try something different and not have to use the Goole Play store all the time.
Beyond Compare - Beyond Compare allows you to compare files and folders.
APK Pure - Download apk for Android with APKPure APK downloader. NoAds, Faster apk downloads and apk file update speed. Best of all, it's free
WinMerge - WinMerge is an open source differencing and merging tool for Windows.
APKMirror - Android Market and APK Downloads
Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.