When I studied CS in university most people used linux laptops or macbooks.
I had a ThinkPad laptop where I would reinstall a new flavour of linux every year or so. Linux is the de-facto standard operating system for web servers and web based apps, so learning linux by using it every day is invaluable.
An alternative is using a Macbook. OSX is based on Unix which makes it largely compatible with, and very similar to, linux. With OSX you pay extra for the convenience of having the operating system work perfectly with the hardware. With linux, you may have to do some extra work just to get your computer in a state where everything works well.