Path Finder

For simple file manipulation, I tend to use Quicksilver (the universal solvent). However, when it comes time for heavy lifting, I turn to Path Finder. This is a hugely useful Finder replacement, even the new, improved Finder in Leopard. It has tons of useful stuff. The cookie trail of where you are in the directory structure? Path Finder has had that for a while. And, you can right click on it and copy the path in a bunch of different formats (UNIX, HFS, Terminal, Windows, etc). And you can click on it to get to the underlying contents of the path. It's tabbed, so you can drag and drop from one tab to the other.

It also has the best (which is damning with faint praise) Subversion client on the Mac (still no Tortoise for the Mac -- rats!). You still have to do serious stuff from the command line, but the Subversion client in Path Finder is great for simple stuff. And yesterday it saved me about 15 minutes of bash hacking because of the "Change Extension" command, which allows you to bulk change extensions of files.

My wife moved (evolved?) from Windows to Mac, and she found Finder too limiting compared to Windows Explorer. But she loves Path Finder. It's one of the first things I put on new machines.