Yahoogroup for Miquon users http://groups.yahoo.com/group/miquon-key/
Discovery oriented math program for elementary only. Uses Cuisenaire manipulatives. Very popular and has been around a long time. Tends to be very inexpensive compared to many other programs.
Maria: I love Miquon. The workbooks really got my children thinking,understanding, and enjoying math. My eldest is now 12 and did Miquon until third grade, along with Math It , and some Calculadder (every now and then). I also used lots of manipulatives to explain the concept of place value.