I always like to "celebrate" finishing a book with my students and take a little break, but I like it to be worthwhile, too.
After Lord of the Flies, we watch Castaway. After Frankenstein, we watch Edward Scissorhands. I like it to be thematically related, but also a just a solid film in its own right to encourage discussion.
Any suggestions for Othello? Maybe something with the theme of jealousy or something with a really strong, manipulative villain???