As hip says, problems from math contests other than MathCounts can be useful. A Well-Trained Mind thread "middle school math contest problems" is at
http://www.welltrainedmind.com/forums/showthread.php?t=190273 .
It's been observed that students who do well in math contests also do well on the math SAT. SAT math prep books targeting good students, such as "Math SAT 800: How To Master the Toughest Problems" or "Dr. John Chung's SAT Math" may help with contest math, although there are topics on math contests never tested on the SAT.
