MacbookPro 3.1 Speed boost : SSD inside !
I am owner of a not so old MacbookPro (3.1 - late 2007), and, as it is my main development machine, I felt a little lack of space and speed mainly because of its hard drive (5400rpm / 160GB).
I wanted speed and so I got a new generation drive with a 120GB SSD, I wanted space so I have dumped the useless SuperDrive from my machine to replace it with a drive caddy (found here) where I have put my old HDD.
The operation is not so easy, but if you are careful and if you take your time, you will not regret what you'll get !
My machine is now blazing fast and it helped me keeping it more instead of buying a shiny new MBP with an unremoveable battery (I think I don't have the feeling with laptop batteries...)