Anyone looking for a simple, (open!) osx music player that just has a playlist you can drop folders onto and nothing else, check out Cog.

http://cogx.org/

Also, Path Finder, a finder replacement in the vain of Directory Opus on windows. It has tabs, split windows, everything you would expect. It also has command line integration and a built in hex viewer/edtior. The only thing I've ever wanted for is regex-based filtering of listings, but I can cope without that.

http://cocoatech.com/

I would go mad without this. Finder sucks.

EDIT: And how could I forget springy, an archiver that lets me double click on archives and actually lets me browse them in their own windows and selectively extract from them, rather than instantaneously spurting files everywhere like every other OS X archiver seems to do.

http://www.springyarchiver.com/

It took me over a year just to find an OS X archiver that behaves like ones on other platforms. It seems mac devs are a little obsessed by mimicking the default apple workflow.