Studyit - Great info on what to expect in the exam for the 3.3 Shakespeare Assessment. Check out the past exams and tips for approaching this section.
Sparknotes - good basic notes on the plot, character, themes etc
No Fear Shakespeare - a plain English translation of the play
Bardweb - very good info about Elizabethan England and anything to do with Shakespeare
Othello Analysis - Some interesting analysis about the source of Othello
Wikiquotes - a nice concise collection of key quotes