Tech blogger Dan Warne notes that MacBooks loaded with serious memory—like MacBook Pros with more than 2 GB—can take a long while to activate these days, since the entirety of that memory is being written to your hard disk in the default "safe sleep." If you're almost always plugged into a wall socket or aren't the type to run your battery down entirely, Warne recomments a one-line Terminal hack that brings back the old swift-moving sleep:
sudo pmset -a hibernatemode 0
If you change your mind or want safe sleep back, run the same command with a "3" instead of "0" at the end. And, as Warne notes, the SmartSleep option panel can customise this a bit, by having your MacBook only activate safe sleep when it's low on battery power.