...something like this:
1. You want to be able to store documents that currently exist electronically, and also handle documents you're going to scan. The latter may, or may not, be OCR'd.
2. You want to attach keywords to the articles, and be able to bring up a list of articles that match some arbitrary combination of these keywords.
3. Full-text search isn't as important (but would be useful if available).
If that's the case, I'm thinking Alfresco might be what you're looking for. Multi-platform, open source, java-based content repository. Supports document tagging (and loads, loads more). Relatively easy to use right out of the box, and has a CIFS interface so you can just create a project and simply tree-copy your current documents into the project. Don't let the "enterprise" designation on the software scare you away.
I've actually considered going that route for my own personal document library, but while Alfresco might be one of the only good solutions, it's like killing a fly with a cannon.
I'm frankly amazed that with the "paperless living" meme currently going through the productivity circles that someone hasn't come up with a simple tool to do something just like what you're looking for: point it at a root folder, let it suck in all the files, then start tagging away. Search with keywords or filenames or both, and provide a clickable list of hits. Full-text search isn't needed, as there's already a ton of tools out there that'll happily index your hard drive for you.
And, if a tool like that exists, could someone point me to it, please?