This site (courtesy of Rita B. Sowell) provides practice with the basic properties. It is a bit elementary, but if you have having trouble remembering which property is which, this site might help.
http://www.math.com/school/subject2/lessons/S2U2L1GL.html
Vanishing Leprechaun (along with a solution).
http://www.angelfire.com/hi2/glasgowgangshow/lepanswer.html