Hi everyone, What I'm looking for are good examples demonstrating torsion in homology. The basic example I know is RP^2, but I suspect there are many more good examples out there. I am interested in the topic both for fun and as part of my research. In addition, I will be teaching a class soon which will involve discussions of homology (in physics). I am primarily a physicist and will be speaking primarily to physicists, so the best examples for my purposes are relatively geometrical constructions, but I'll take anything you can give. Also, I would personally be interested in excellent (pedagogical or otherwise) discussions of the topic even if they are primarily mathematical. Thanks very much!