Believe it or not, but the Mac OS X trash can did not have the ability to send files back to where they came from; you had to manually copy/paste/drag them back to their original location. In the new Snow Leopard builds, a feature called "Put back" has been added, which will move any selected files from the trash back to where they came from. Users who remember Mac OS 9 and earlier will know this features as "Put away".
The Stacks feature in Leopard has always received many, many criticism for being rather limited in its functionality. One of the most often requested features was the ability to navigate the directory tree from within the stack, without having to open a Finder window. In Leopard, clicking a directory in a stack would simply open a Finder window; in Snow Leopard, it will shrink the original 'window' to a small representation in the top-right corner.
Snow Leopard might be a performance and maintenance release, but that doesn't mean Apple isn't applying some fixes and adding some small features here and there as well.