The standard is 2GB of RAM, however, even though apple won't confirm this, with the late model 2.4GHz you are capable of upgrading to 8GB of PC3-8500 DDR if you're on snow leopard and have the updated boot ROM version MBP51.007E.B05 which you'll find under the "About this Mac" extended view. I recently installed the upgrade and it works great. Something to consider to optimize performance.
"*Apple officially supports a maximum of 4 GB of RAM. Originally, this model was only unofficially capable of stably supporting 6 GB of RAM, but as confirmed by site sponsor OWC, it is capable of supporting 8 GB of RAM if updated to Boot ROM Version MBP51.007E.B05 and running MacOS X 10.6 "Snow Leopard."