TagBot

TagBot: File Tagging For Mac OS X. Because Tagged files are easy to find - no matter where you put them.
- Tag your files by right-clicking them in the Finder...
- Find all files with a given tag by double-clicking the tag...
-...or by dragging them onto TagBot's tag palette.
-...or find them using Spotlight.
- Tag your photos with names and locations.
- Track invoices and other work documents with status tags.
- Organize your AddressBook entries.
- Categorize graphics, sounds, and other media files with descriptive attributes.
Free for unlicensed use with up to six tags. To use more tags, purchase a license for $20 through TagBot's built-in store.