Transcription (Biology)
DNA Transcription 
Short animation rich with information about DNA transcription. This definitely helped me out in a bunch of my biology courses. Reading your textbook beforehand is a plus, but definitely not needed to understand the basic concept.
Replicative Transposition Animation 
Really cool animation that helped me understand transposition. This animation gives you the option to choose between wild-type or mutant pathways. This animation shows the transposition of the E.coli Tn3 transposon.
