Hi Ken, thanks for getting in touch.
Daniel put together some pretty nice code (which, for easiness, you could place in your theme’s functions.php file) that might be of interest here:
https://gist.github.com/3415684
The way that piece of code works is to hide any events assigned to the special “hidden” category. I would imagine you could extend this and add as many different categories as you wish (the line you would need to edit being line 15).
I appreciate this is effectively the inverse of what you are after, but it might let you achieve the same effect. Alternatively, if you are confident working with code, you could probably take Daniel’s code and bend it to your requirements.
Hopefully that gets you on the right track – and let us know how you get on!