Wake Up Your Mac Faster: "You can change the Mac’s hibernate behavior using pmset; here’s the reference for it:

http://developer.apple.com/documentation/Darwin/Reference/ManPages/man1/pmset.1.html

“sudo pmset -a hibernatemode 0″ = suspend to RAM only (default on desktops)
“sudo pmset -a hibernatemode 1″ = suspend to disk only
“sudo pmset -a hibernatemode 3″ = suspend to disk RAM (default on laptops)"