Chrome Web Store - Chrome Web Store is an officially recognized application store being developed and managed by the Google.
Mozilla Add-ons - Download Firefox extensions and themes. They’re like apps for your browser. They can block annoying ads, protect passwords, change browser appearance, and more.
Chrome Extension Downloader - Chrome Extension Downloader is the name of a website dedicated for downloading and Chrome extensions.
Addoncrop - Extends the functionality of your web browser
Opera Add-ons - Get extensions and themes for the http://alternativeto.net/software/opera browser.
cloudHQ Chrome Extensions - cloudHQ Chrome Extensions is a multipurpose platform offering services from cloud data management to apps for Google related products.