Gore, anybody other than Lieberman.
Kerry was on the list and he could help clinch New Hampshire (but he might swing places like New Mexico, Oregon, Iowa, or Wisconsin red).
Shaheen helps flip New Hampshire and being a woman likely helps with women.
John Edwards was on Gore's list. He pleases liberals and southern populists.
Graham helps in Florida.
Dick Gephardt is another moderate from a southernish state, so I'd say he works - especially if he flips Missouri.
For Bush, John Danforth was the preferred backup to Cheney IIRC.
George Pataki was also on the VP list too I think.
For Nader, find a very progressive journalist with solid name-id and good media ties?