Kerry's choice for some of these positions will depend on who he chooses as running mate. That said, here are some people I'd like to have a cabinet position, assuming (a very large assumption) that John Edwards is the VP nominee:
Secretary of State Wesley Clark
Secretary of Treasury Franklin Raines
Attorney General George Mitchell
Secretary of Defense Carl Levin (or John McCain)
Homeland Security Chief Sam Nunn (or John Warner)
Secretary of Labor Dick Gephardt
but most importantly...
Secretary of Health and Human Services Howard Dean