We're flying to Spain from Texas on Thursday, March 21, and out on Monday, April 1.

Any one have any favorite airlines to recommend? Or know of good deals?

Continental has great service from Texas thru Newark to Madrid and their prices are very competitive. I recently flew on their new wide body B-777 between Newark & Madrid!

I have seen consolidators offering cheap seats in the past on KLM from Houston to Madrid via Amsterdam.
Also, because of the recent partnership agreement between Continental & KLM, you can earn double Continental One Pass miles on all KLM flights thru the end of March. Thus you earn enough miles on say a RT from Houston to Madrid which you can cash in for a free domestic US RT ticket!

When I went to Spain, I flew from Dallas to Brussels on Sabena and then took a flight to Barcelona (I think on Iberia). That was the best deal that I found at the time.