A while back, I began implementing tags on the website, both for blog posts and such, and KSP crafts. Just now, I finished implementing a sorted list of all tags in use on KSP crafts, so you can look through them via this list.
I still have to implement the ability for users to add tags to their own crafts, and eventually a concept of “trusted” users who can tag anyone’s craft, but for now, you can look through craft via some of the tags I have added.