RAM that can handle OCing fairly well would be something like Kingston HyperX brand, or Corsair XMS. These chips come with heat spreaders, and are built to good standards, which make them OC-friendly
OCZ is currently top quality. Outperfoming Corsair which outperforms kingston on both performance and Overclockability. Plus they look ultra sexy with their mirror finish polished platinum heatspreaders.
But heatspreaders is contraversial right now. There's a brand of RAM that has great OC'ability but doesn't put heatspreader on theirs, so many speculate they really do nothing. I forget the name that doesn't put heatspreaders on...starts with an F I believe but I can't think of it right now