Maths

http://www.funbrain.com
An interactive teaching resource which fully supports both assessment and revision. The levels are American but the content is relevant.

http://www.samlearning.com
Similar in style to Bitesize, but drag and drop tests are available for most subjects.

http://www.bbc.co.uk/revision
An excellent site for many subjects including maths.

http://www.maths-help.co.uk
Maths Help offers impartial help and advice with problems in Mathematics and Statistics. It is mainly aimed at UK students taking maths at GCSE, A-level, GNVQ, BTEC, Access or Foundation year degree level (or equivalent). Got a problem? Go to the Send Us a Query page. Within 24-48 hours (maybe a little longer at weekends and during holidays) they should email you back with hints and suggestions which should help you to make progress.

http://www.bbc.co.uk/education/revision
What the BBC claims to be is the 'first ever revision guide via TV, books and the Internet'. Bitesize is a nicely produced site, with slick graphics to guide you around. As the name suggests, the site doesn't attempt to talk you through endless reams of text - there's very little point in that approach online anyway - but instead provides digestible, bite-size gobbets of information to assist your GCSE revision. The list of subjects covered is impressive: business studies, design and technology, religious education, maths and Spanish to name just five.