PloneKeywordExplorer provides an alternative to the usual Plone search.
The search is iterative. Keywords can be added and removed from the search at any time, allowing the user to conveniently explore the document space. The result set can be narrowed down to a few documents in a few steps.
PloneKeywordExplorer depends on well-chosen keywords, and supports finding documents that don't have keywords associated. When you click on the [no keywords], you get a list of all documents that do not have keywords. You can browse through this list and start annotating your documents.