Yes you can :)
Just installed Silicon Power 4Gb RAM clocked at 1333MHz on my MacBook late 2009 model and it works just fine.
To note that since it was the last RAM module available @ the reseller, I've installed both a 4Gb RAM (1333MHz) and the OEM 1Gb Ram (1066MHz) and my system is working without any issue.
looking @ the system info you'll notice that the clock speed of the Ram is 1066MHz. IMO the 1333MHz has been down-clocked to 1066MHz by the system.
I've already planned to get another 4Gb Ram to get the MacBook to a total of 8Gb of RAM.