If you’re really serious about managing your photos you should get a proper cataloguing application. There are a few out there. Neither is really, really good (but which software is that?). It’s not cheap but useful. You can typically try-before-you-buy. The two I have looked at and find useful are these two:
Extensis Portfolio
The publisher’s site
iView MediaPro
The publisher’s site
Both these two have surprisingly similar functionalities, so much so that I’d almost say that it doesn’t really matter which one you choose. Some things are different though. The user interface feels more “modern” on iView MediaPro perhaps. Portfolio on the other hand has a better (safer) way of updating the database (done at every modification). Portfolio has a clever function of assigning keywords to pictures by dragging and dropping from another application (e.g. Microsoft Word) which is very, very useful. On the other hand it has a bug that truncates the keywords after just over 1000 characters when the software writes it in IPTC metadata on the file (which, of course, is only a problem if you use large numbers of keywords). (At least in version 7. Perhaps it is fixed in version 8?) Both have good user forums (an independent one for Portfolio) that give good support. For me, Portfolio comes out slightly on top thanks to the keyword drag-and-drop feature (its a BIG, BIG plus (for me) actually). From a corporate perspective MediaPro seems to be a much more dynamic company though (Extensis do need to get a bit more reactive IMO). Then again, iVeiw MediaPro was recently bought by Microsoft, so we’ll see where that leads…
Both have trial versions that you can try for free. So you can decide for yourself.