Ideological Composition of the Congress
Above is a great picture of the composition of the House and the Senate. It uses DW-Nominate scores which political scientists have been using for years to study the Congress. The site does a great job of explaining the ideological breakdown. If you want something really cool, go here and you can see how the ideology of the Congress has changed from the first one to the current one. It is put together by noted political scientists, Poole and Rosenthal. It is really cool to see how we have become much more ideological in the Congress as time has gone on.