Here are some examples of school/college careers web sites. Some are good, some are poor but all have features that are worth noting as things to do, or things not to do:
Ashville College Sixth Form
Brentwood School
Benjamin Britten High School
Cavendish School
Ilsley School
Priory School
St Mary's High
The Woodroffe School
Tring School
Thorpe St Andrew High School
Wiltshire College
...and here is one from a Connexions service
Here are some links to web based careers resources. Each is a catalogue of web links that you can use to find stuff that might be worth adding to your site:
The Careers Gateway - free with lots of links to careers and HE web sites
Career Companion - a priced resource (from £10 per year) includes reviews of web sites covering all areas of careers and support.
Finally use the Virtual Libraries link on the right hand side of this page to see some advice and guidance from those nice people at Connexions Nottinghamshire.