Tab Mix Plus

My friend has just started to try Firefox after he noticed that that 2.0 version has come out. Before this, he preferred Opera as his browser. Before he start migrating to Firefox, he would like to look for some extension which will bring Opera's features to Firefox and one of them that he showed me was Tab Mix Plus, a small simple extension which can extend Firefox's tab feature. This is a simple description of Tab Mix Plus from their website:

Tab Mix Plus enhances Firefox's tab browsing capabilities. It includes such features as duplicating tabs, controlling tab focus, tab clicking options, undo closed tabs and windows, plus much more. It also includes a full-featured session manager with crash recovery that can save and restore combinations of opened tabs and windows.

So if you was an Opera fans and you would like to have Opera's tab feature in Firefox, the probably you will definitely install this extension.