The New American Foundation just put out one method that California could use to make its legislature more representative (pdf).  It looks like a regional form of mixed member proportional representation (MMPR).  MMPR is used by Germany to elect the Bundestag (i.e. parliament), and by number of other countries such as New Zealand, and in Scotland and Wales.  Various Canadian provinces have entertained adopting it as well.  I highly recommend that folks read the report if they are interested in changing our seriously flawed electoral system.