Nostalgy is an extension for Mozilla Thunderbird whose purpose is to save time by doing more operations with the keyboard. If you want to use Thunderbird without sacrificing the productivity you had with good old mutt/pine, this extension is for you!
Nostalgy adds keyboard shortcuts to change folder, move/copy messages, with folder name auto-completion (using only the keyboard). Also includes a system of rules to suggest a target folder for saving messages; re-creates Eudora's Alt-Click; facilitates navigation in the 3-pane window; makes it easy to change between To/Bcc/Cc fields in the composer. All that with the keyboard only!
Other keyboard actions include: changing focus between panes, scroll the message while keeping the focus on the thread pane, changing header in the composer (To/Cc/Bcc), adding an attachment, hide the folder view.
The easiest way to install Thunderbird is through https://addons.mozilla.org/en-US/thunderbird/addon/nostalgy/ . It will automatically update itself when new versions are released.
You can also try the latest development version from http://alain.frisch.fr/info/nostalgy-current.xpi