This is from the work I've done in my dissertation. This chart shows the level of partisanship between the political parties in the Texas House of Representatives across 18 years of record voting (otherwise known as "roll call votes").
The center line, at 0 should be your reference when viewing this movable chart. The further away a party is from this center line, the more partisan their voting behavior. To help simplify this, the bigger the circle, the less bi-partisan they are.
I've collected all the roll call votes from the Texas House of Representatives from 1991 through 2009. Then I use a dimensional scaling method, W-NOMINATE from Keith Poole's VoteView research. I also do some creative aggregate calculation for the political parties and "Speaker's Teams", and squeeze in a nifty little trick from Gerald Wright that applies a Groseclose-Levitt-Snyder transformation to get all the sessions within the same scope.
[Updated with 2009 data.]