Try exploring the following links. Some are useful for particular topics, others for general biology and some are useful for revision.
http://darwin-online.org.uk/ a useful site to discover the origins of Darwin's work
Useful animations for many AS and A2 Level topics
Useful for Unit 1 work on Cells
Useful for Unit 1 Organelles, DNA replication and Mitosis
are useful tutorials for Unit 1 Transcription and Translation