Microsoft offer a number of different options for students, development software such as Server operating systems are free through the Dreamsparks website, general consumer software such as Windows & Office can be bought at significant discounts through the Digital River & Software 4 Students sites.
Dreamsparks is a site specifically designed to give budding software developers the tools to create applications for the entire Microsoft eco-system. It now includes tools for developing apps for the new Windows Phone operating system, as well as using the fantastic Kinect system to recognise movement & gestures without the need to come into physical contact with the computer.
The Microsoft Mathematics software could be useful for students studying any Maths, Science or Engineering courses but will obviously need to be run within Windows either via Boot Camp or through Virtualisation.
The Windows Server downloads are potentially a great way to get a copy of Windows to run on your Mac, they can be installed in any of the virtualisation software described in the Windows on a Mac section of this site. Although the software is designed to provide server connections for multiple computers it will run all the software you need to and although lacking some of the consumer orientated features and ease of use that Windows 7 provide the Server options from Dreamspark are free.
Software 4 Students
Other Microsoft software is sold through the Software 4 Students website, this site is a Microsoft Authorised Education Reseller, they offer Windows & Office at significant discounts of 80-90% in some cases.