The quickest way of accessing your @cam.ac.uk email is through the secure Hermes Webmail page. You can use this from any computer with a web browser.
On the College MCS computers, just type 'hermes' in the username box and press return. Note that if you use this option, you won't be able to browse the internet or edit documents, but if all you want to do is read email this gets you logged in much quicker than logging on to your MCS account.
Hermes Webmail is the easiest way, but if you would rather not use that then good email programs are Mozilla email (included within the Mozilla browser) and Mozilla Thunderbird (an even speedier version) which are available free of charge. Configuration instructions from the University Information Services for non-Webmail email applications are here.
Applying for email and extra space, and other email notes
The University Information Services email page gives many other details such as applying for and finding email addresses, requesting an increase in your Hermes quota online and other useful notes. If you are getting a lot of junk mail, see here for advice, and try adjusting you your settings on the University's spam filter.