[Haskell-cafe] Programming with categories

Hi Haskell-cafe. I'm trying to use Haskell to program with Categories, but I didn't have seeing some works in this area nor references about this. Does someone can help me ins this subject? Thanks in advance, Vieira -- "Para saber quantos amigos você tem, dê uma festa. 'Para saber a qualidade deles, fique doente!"