SumDog.com - Great website with tons of math games! This is a favorite every year.
Cool Math - This website has good brain games that integrate math.
Sample STAAR Questions: - This site has a few STAAR type questions to give you an idea of the rigor of the test.
Education Galaxy - STAAR practice that requires an account.
BrainPop - Great site for instructional videos!
Wolfram/Alpha - Knowledge Engine that shows you the answer to any problem. Great resource for checking whether or not your word problem is solvable!
Think Through Math - Great website that gives the students lessons based on their needs.