One of my faves is Gov. Bill Richardson (Democrat-NM). The former Congressman, U.N. Ambassador, Energy Secretary, and global deal maker easly "out-resumes" every other announced candidate.
Even former Rep. J.C. Watts (Republican-OK) and conservative columnst David Brooks think the guy would be a formidable president.
This is not an endorsement, but at this point Bill Richardson is probably the Democrats' best candidate.