Ammonite lets you find tagged files quickly. It works with Mavericks or OpenMeta and supports DEVONtechnologies' excellent product DEVONthink Pro.
Ammonite visualizes the tags used in a database and on your filesystem. Tags applied to many documents will appear larger than tags applied to a few documents. This helps you to drill down on the information you are looking for. It visualizes dates, file types and "nested tags" in separate clouds as well, providing a unified, intuitive interface for building even the most complex queries.
Ammonite is easy to use: left-click on a tag in the cloud to find documents having this tag applied, right-click to display documents not having this tag. Combine as many tags in your search as you need. The result is updated immediately. From here you can reveal or open them in DEVONthink, Finder, or an external application. QuickLook is supported.