AlternativeTo - AlternativeTo lets you find apps and software for Windows, Mac, Linux, iPhone, iPad, Android, Android Tablets, Web Apps, Online, Windows Tablets and more by recommending alternatives to apps you already know.
start.me - A Modern-day bookmark manager. A place for your favorites. A news feed (RSS) reader. A browser startpage. A portal for your team.
Ruby Toolbox - Explore and compare open source Ruby libraries
Netvibes - First personalized dashboard publishing platform for the Web. Digital life managment, Widget distribution services and brand observation rooms.
LibHunt - LibHunt tracks mentions of software libraries on relevant social networks. Based on that data, you can find the most popular projects and their alternatives.
All My Faves - Visual homepage that specializes in logo-based bookmarks and in the best top 10 sites of each category. This ultimate homepage makes the Internet an easier place.