MMP
From Voteswap Canada
MMP or mixed-member proportional is a class of voting systems often proposed as part of an electoral reform. It competes with STV, 123 and new systems like BSTV+C+L to replace the FPTP system presently used in all provincial and federal elections within Canada. See "the frustrated voter" for a detailed comparison of various types of balloting systems with illustrations.
Two referenda were held in Canada on adopting this system, in PEI 2005 and Ontario 2007. In both cases the referendum failed miserably with only about 38% of the vote, out of a required 60% to approve. For details on the referenda see PEI electoral reform referendum, 2005 and Ontario electoral reform referendum, 2007. Because of this MMP is not considered a viable electoral reform for Canada - especially those variants of it employing closed list selection of candidates by the parties not the voters directly. Or any unclear proposal such as Ontario's where it is possible that the parties will be allowed to do this, or to set their own "democratic" mechanisms to select cronies.
For details on its mechanics see Wikipedia.
See "the frustrated voter" for a detailed comparison of various types of balloting systems with illustrations.