Today, Canon announced their latest flagship camera, the EOS-1Ds Mark III. I hate to be one to compare megapixels, but this camera is up there, weighing in at 21 megapixels. That's basically the quality of traditional medium-format cameras. However, that power comes at a high price tag of $7999 (body only).
For more information, you can see Digital Photography Review's preview by clicking here.
And if you're working on a slightly smaller budget, you might want to check out Canon's 40D, a very nice pro-sumer level camera. It seems to be the equivalent of Nikon's D200. You can find its preview at DPR by clicking here.
Alas, poor Nikon, always the bride's maid...