Here are some useful websites with past papers and exam questions arranged by topic.
XTremePapers is not a specialist Physics site but it has an amazing array of papers on most subjects plus an interesting set of discussion forums.
MathsMadeEasy has a selection of past papers plus some very useful topic specific questions.
CIE Notes has an amazing collection of notes and past papers relating to the Cambridge AS and A Level Specs and also to Pre-U.
PapaCambridge. Lots of past papers here.
Physbot has a selection of written answers to exam questions arranged by topic.
Studymind has a very useful set of questions arranged by topic.
Here are some useful websites with revision notes
A-Level Physics Tutor has some excellent topic notes and even a complete set of e-Books.
Save My Exams has a good selection of questions arranged by topic.
S-Cool has a very good selection of revision resources, but you will need to register first.
Here are some multiple choice questions you can use for practice.
Gorilla Physics has lots of useful revision resources including videos.
O A Level Notes has an amazing array of topical questions and revision notes.
Physics Tutor Online has a comprehensive array of revision notes.
FastExamPapers has a very useful set of revision notes.
This is an interesting blog site which has exam questions with solutions relating to Cambridge exams.
Another great set of resources here.
There is a comprehensive set of excellent Physics quizzes here: