The vector space search looks like it could possibly handle what I need, although if it keeps everything in-memory, it's going to eat up a ton of resources (it would have to parse the entire group of documents each and every time the script is run). Perhaps using the Storables method above along with this would be a good solution.

The other difficulty (and why the amazon-method would not work) is that this is an auction site. It is very unlikely that two people would ever purchase (ie, win) the same item with the exact same title. And because it's an auction site, those 5,000 or more items will not always be the same 5,000 items. In fact, the turnover rate would be in the hundreds-per-day.

Also, these "documents" would of course be contained in a database. I'm not sure how much that throws things off. I suspect it doesn't from my reading of the article you linked to.