The NRMP has published data from the 2009 Match, including "PGY-1 Match Rates" and "Number of PGY-1 Positions Offered and Filled for Selected Specialties." It's almost too much information for future residency applicants, but candidates can look through the doc to see what interests them most.
Here's it is: "Results and Data: 2009 Main Residency Match."