TotalFinder by Binaryage, is a plugin to the Apple Finder and adds Tabs, Side-by-Side Finder windows and convenient access (key driven) to Finder in any application.
I found TotalFinder in the MU Promo bundle and didn’t need the other software, so I grabbed it from the dev’s site. I use Finder a lot and will be making good use of the tabbed windows. The key access driven “visor” as it is called makes Finder available all the time with a press of a keyboard key. TF is compatible with OSX Lion. It may not seem like a necessity, but once you use TotalFinder, you will wonder how you got along without it.