Good opera pieces for baritones?

I'm considering the idea of teaching myself a bit of opera, what would be some good pieces for a baritone to learn? If I can get a knack for it, I may try to get lessons. Thank you for any and all help :)
Update: I understand that, I've sang in many other fields before so I'm curious how good my voice is without classical training. This is almost a challenge for me, I know I'm not going to master it, I'm just trying to see where I measure up with this.
4 answers 4