Sure just make a few partitions install the OSes and delete the OSX partition.
You will need to download Windows drivers first and for 7 you need to create the MBR partition. Linux can run on the normal GPT partition.
Then you switch between them by holding down the option key at boot. I haven't tried it but I am pretty sure that should work. Though I think OSX is the best OS on a Mac. The Touchpad sucks in Windows and you'd really be better served with a Windows notebook with decent Touchpad drivers. The Trackpad++ driver makes a bad thing not quite as terrible but it is still far from a proper smooth driver.
I don't even know how the driver situation looks in Linux.