AniDB

It would be nice if, as an addition to the categories, users could stick arbitrary single-word tags on each anime. There will always be more potential catagories than would be reasonable to put in the "official" list, but letting users pick their own actually tends to work out pretty well....

Nope, it can't be done with CSS (on the user end), as the required information isn't there. Too bad - otherwise it would be fairly simple.

The anime calendar, at least, could be fixed with a greasemonkey script. I'll leave that as an exercise for the reader.