Originally Posted by CPRich
I know I'm in the minority, but I still prefer Netscape. That "New Tab" button just to the left of the first tab is just so useful that not having it bugs me whenever I use Mozilla or Phoenix/Firefox.
Ctrl-T opens a new tab in FireFox. I use it all the time.
Even more useful, though, is when you click any URL, Bookmark, or Favorite, hold Ctrl when you click, and the URL/Bookmark/Favorite opens in a new tab.
I'd repeat a bunch more keystrokes, (such as Ctrl-n, changes focus to the n-th Tab), but they are nicely summarized here:
Firefox Help - Keyboard Shortcuts. This shows a very useful comparison to the equivalent keystrokes in IE or Opera, so if there's something you can do in one browser, this matrix shows you how to do it in the two other browsers.