I really like the NLVM website.  There are many user friendly actvities and most of them kept me engaged.  The activity that I would use with students is the Algebra Balance Scales – solving simple linear equations using a balance beam.  First,  you need to move the tiles to rewrite the equation.  Then, you solve the equation.   I would use this as a follow up activity for solving equations.  You can also use it as a warm-up projected on the white board.

http://matti.usu.edu/nlvm/nav/