Classes that aren't models or libraries

[eluser]Hypnotoad[/eluser]
If a class is very application specific, would you consider it a library?

I suppose I could put them in the libraries directory, it just seems like the wrong place.

Is the libraries directory only meant for libraries loaded with $this->load->library? Would you consider it correct to put other classes in the library directory even though they are not used as libraries and instantiated manually within models?