If you asked congressional experts what legislative subjects, say, Sen. Patty Murray of Washington specializes in, they’d have a few pretty good guesses: maybe education and health care — because she’s the ranking member on a key committee that oversees those issues. If you asked who else in the Senate shares her interests, you might hear Sen. Michael Bennet of Colorado. Why? Because he is a former school superintendent and a member on that same committee.
Interesting site; looks like it would be useful if you wish to follow specific legislators.