As Shane said, it's physically possible to take the drive out of one PS3 and into another but it won't preserve all your data. Use the transfer utility, it works quite well and if you've only got a few things then it won't take too long.
Another way, depending on what you want to save, is to backup your saved games etc to a USB hard drive and then copy them to the new PS3. You can't copy everything, but by-and-large you can copy everything you can't replace by downloading again.