Something I haven't realized was that the Adwords API returns one or more categories for every search term you submit. Now you can filter domains using those categories. You can find the filter under Adwords & SEO Filters. Alone the filter is not very useful, but if you combine it with the other Adwords filters it might help you out.
At the moment only the first two levels of the category tree are used in the filter select box, but the domains are tagged using the full category tree. I've decided not to use the full category tree, because it is huge and I'm not sure how usable it is. You can check it out here. You can take any ID from the list and replace it in the url to test it out (eg. &fadwordscategory=10021).
It is only running for a while now, so not all domains are tagged yet.