The first of the following two sites is more activity-oriented, the second more games. The first is a general website and has subjects other than mathematics.On the first site, it may not be obvious how every activity relates to mathematics, the site's author assumes that many know, for example, that cooking and following a recipe involve math and logic/sequencing skills. On the second site, there are several Jeopardy-type games on many middle school mathematics topics (factors, LCM, LCD,integers, etc.) that can be played solo or as teams in a classroom.
http://www.education.com/activity/middle-school/math
http://www.mathplay.com/Middle-School-Math-Games.html
