You know how stuff like animations, games, art, audio and the like all have tags so it's easier for people to find what they're looking for? Well why not do the same with threads? The OPs could have the option to add up to 4 tags to their thread while he or she is writing their openning post, this would be the one and only time that they'd have the power to do so as after they've clicked post they lose that priviliege (or maybe they're still allowed to change it in a 15 minute window?), moderators on the other hand would have access to edit those tags at all times, be able to add/remove/replace tags as they see fit if the OP didn't tag it properly.
It might be an easier way for people to look up if there's been any recent thread on the subject they're interested in.
Any thoughts?