Prime factoring tree (basic): http://www.mathgoodies.com/factors/prime_factors.html
Aim and shoot at the factor, multiple as well as the prime/composite number: http://www.toonuniversity.com/4m_prime_d.html
Jeporady review game for factors, multiples and prime factorization: http://www.quia.com/cb/8436.html
Teacher Links
http://www.pbs.org/teachers/mathline/lessonplans/pdf/msmp/factor.pdf (directions for file folder game-factor capture)
http://www.math-aids.com/cgi/factor_trees.pl?max_num=0&language=0&memo=&answer=1&x=76&y=8