Today's New York Times has a nice overview of the complicated geography, demography, and delegate math in next week's Texas primary. Also, a nice graphic to go with it.
One of the best blogs on Texas politics provides a look today of early voting results (in terms of turnout) so far. The numbers clearly suggest a much larger electorate than in previous Texas contests, mirroring what we've been seeing across the country. He also provides an excellent discussion of the allocation and distribution of delegates for the Democratic race.