How do you find a list of CMMI certified companies?

For the years 2005 2006 2007 2008 you can go to http://sas.sei.cmu.edu/pars/pars.aspx.

Here you can select your desire year/model result from above link.

Or

For Level 3, you can to to http://sas.sei.cmu.edu/pars/list.aspx?ml=3