I have a lot of problems with Finder. It does things I don't want, and it doesn't do things I do want.
There are seemingly two ways to approach this problem: replace Finder and extend Finder.
In theory, I prefer the "replace" approach. In practice, though, it doesn't work all that well. While there are apparently hooks in the OS to have another application handle what would otherwise be Finder requests, enough applications seem to hard-code Finder to make side-by-side replacement be annoying, at best. And completely replacing Finder.app is apparently bad juju.
So the practical thing would seem to be Finder extensions. Is there a list of them somewhere? If not, can we make this a list?
Also, can multiple extensions be loaded at the same time?