I have been testing Slideboxx over the past day (Windows-only). Slideboxx is a tool that crawls all PowerPoint files on your computer (it counted more than 5,000 on mine…) and stores visual thumbnails and keywords of all the slides in a searchable database. You type in a keyword, you get instantly served icons of matching slides with options to refine your search, find similar slides, and even “frankenstein” (what?) a new presentation from old slides.
First of all, there is a real need for a tool like this. The legacy Windows filing system based on file names and application icons is useless for visual files such as PowerPoint slides. I am now using Gmail to track down presentations (“where is that file I sent to [x] a month ago?”) because a date, a keyword, and a person is a better clue to what I am looking for than a location on a hard disk.
There are more companies developing professional solutions to dig through data stored in enterprise networks, not just PowerPoint, but including spreadsheets, PDFs, databases, etc. BA Insight is one for example.

Back to Slideboxx. The software is easy to install, the interface is nice and clean, and the program is very powerful to dig up long-forgotten slides.
For someone with a lot of slides who makes presentations for one company, or related to one subject area, the tool makes a lot of sense, and could actually be a significant time saver.
For my 5,000+ files the search results are sometimes a bit too broad, I would love to have an option to narrow searches actually by a folder on a hard disk. Another approach would be to add generic presentation tags to all slides in a presentation. For example the company name on the front page of the deck, the name of the presenter, the subject of the presentation, the items of the agenda, each of these are relevant to all the slides in a presentation, while they might not be written down explicitly on each slide.