Smart Folders for Mac

From Rage:

Smart Folders creates a special kind of folder that will search your entire hard drive and find all items that match certain criteria that you specify. It can update itself at certain intervals to make sure it is always up to date. Your files and folders will all be located in a central location so that you do not have to go hunting around your computer for them. Best of all, its fast and easy to use since it doesn't have to copy or move large files across volumes. Instead it creates aliases which are just as good as regular files but without taking up extra hard drive space.