Mark Kleiman lays it out for them:
Anything that can be ridden on the Defense Appropriations bill (or on a continuing resolution) doesn't need 60 votes in the Senate. It needs 51 votes in the Senate, or 218 in the House, that will stand firm.
Take, for example, the Webb Amendment, forbidding troops from being required to serve tours in Iraq longer than the spells between tours. If passed, it would force a troop drawdown by spring.
The Democrats should offer the Webb Amendment when the Defense Appropriation comes up. If the Republicans want to filibuster, fine. Don't pull the amendment. Just let them keep filibustering. As long as the amendment is on the floor, there can be no vote on the bill itself. Keep calling cloture votes, one per day. After a few days, start asking how long the Republicans intend to withhold money to fund troops in the field in order to pursue their petty partisan agenda.
If the Republicans in the Senate hold firm, it's their stubbornness that's holding up the bill. If they fold, and the bill gets to the President's desk and he vetoes it, then pass the same damned bill again. And start asking how long the President intends to block funding for troops in the field in order to pursue his petty partisan agenda. Read on...
See? Congressional Democrats, take note. Rather than retreat back into the battered spouse routine you've got perfected, do your part to act like the majority party. I promise you'll see your collective approval ratings shoot up.