Hawkscope is a productivity tool that allows you to access your hard drive contents quickly via system tray / menubar icon with dynamic pop-up menu.
Completely Free and Open Source
Cross platform, runs on Windows, Linux and Mac
Navigation through hard drive contents via dynamic popup menu
System wide global hotkey for invoking menu right under mouse location (on Windows and Linux only)
Configurable favourite locations for quick access
Hide unwanted drives, folders or files by adding them to blacklist