The Twins really only need to build a core that is essentially untouchable (unless they are blown away which is unlikely).
Right now I think that group is Mauer, Diamond, Burnett, Plouffe, Dozier, and Revere. Nearly everyone else becomes expendable for a reasonable price. I think we have two groups of trade bait. One is "As Good as Gone" and the other is "Moveable". The Difference is that the AGAG absolutely NEED to be traded, while Moveable pieces still could be part of the Twins future and would need to pried away.
AGAG: Doumit, Carroll, Span, Burton, Capps, Swarzak, Liriano, and Pavano (If anyone wants him)
Moveable: Morneau, Perkins, Duensing, and Willingham