Lots of websites use class names like floatleft, clearfloat, alignright, small, center etc that describe the
Style classes should be semantic. This is a great article on semantic web page design (well, I found it really helpful anyway).
EDIT: I just read another article that makes some good points for using things like display: inline-block, display: table etc. instead of floats. That should help avoid those pesky floatleft and clearfix classes. Making them semantic is always up to you though.