Tags
Extend your Finder with tags, to find your files in multiple ways.
... on top of a Tag icon to add it to that Tag. Double-click a Tag to view all items that you added to it. Remove items from a Tag by dragging them to the Trash. Or remove the Tag itself by dragging it to the Trash. Tags are just like folders in many ways; you can even tag Tags!
The software works on Mac OS X 10.4 and all higher versions. Have a look at the screenshots to inspire you, and make sure to read the Readme that is included with the download, because it's really helpful.