Became a commercial solution not long ago: the full beta development stage was free and gave me plenty of time to test the software. It's an excellent solution, and I have seen almost every single bug disappear progressively. Even if not a free solution anymore, its source is available on GitHub. I would recommend it on the grounds that it already works wonderfully well, and definitely deserve some support in my (otherwise freeware-oriented) opinion. If freeware is yet a compulsory feature for you, Geekosaur's link has a few options.

One Commander Alternatives

Edit, 2013-01-07: as mentioned in another answer, looks like TotalFinder, but free. I am satisfied with. Although it costs $20 after trial period, it is a simple yet powerful replacement of Finder/Total Commander. What I value the most over other alternatives:. Simple and clear UI: power is under the hood. Easy switch between 1 or 2 panels (mostly I use only one). Option to setup shortcuts: Enter to open file, backspace to move up.

Regular Expression for filters. Renaming multiple files.

Sync folder: showing added/deleted/modified files. WebDav is much faster then in Finder See for all features and screenshot.