Splash Mountain or Thunder Mountain (whichever line is longer) get the fastpass for the longer line and ride the other while you wait for the fastpass window.
Space Mountain
If you're doing Fantasyland, Peter Pan normally always has a long line.
Tower of Terror or Rock n rollercoaster, (same as Splash/Thunder, get one for the longer line, and ride the other one)
Expedition Everest
Soarin
Test Track
Those are the ones I normally fastpass because the lines are so long.