FileInfo.com - FileInfo is the central file extensions registry and contains a database of over 10,000 file types.
DockbarX - DockbarX is a standalone dock that groups and launches applications.
File-Extensions.org - Large computer file extension library with detailed explanation of each file type with links to download free or associated software programs.
Synapse - Synapse is a semantic launcher written in Vala that you can use to start applications as well as find and access relevant documents and files by making use of the Zeitgeist engine.
FILExt - Open, view and convert files online
Gnome Do - Simple, sleek, swift, smart. Do. GNOME Do allows you to quickly search for many items present on your desktop or the web, and perform useful actions on those items. GNOME Do is inspired by Quicksilver & GNOME Launch Box.