1. Practice a passage backwards. This challenges you to read from right to left and also to use the reverse muscles to produce the movements. You have to hear the intervals backwards. It's a really great way to make sure you know your shifts, in particular. I learned this from my high school teacher, Lisa Cridge.
2. Reverse all of your bowings. Take a passage that starts downbow and start it up bow. BUT, strive for the same quality of sound and the same phrasing. From my teacher Burton Kaplan.
3. For fast sixteenth note or triplet passages that are normally played off the string (such as the Mendelssohn Scherzo): Play them with reverse bowings, on the string, at the tip. You use different muscle groups, but you're putting the same notes in your brain. From Herbert Greenberg, former concertmaster of the Baltimore Symphony.
4. Plug your left ear with an earplug or tissue paper. Seriously. This forces you to listen to the sound coming back to you with your right ear, rather than listening to the sound that's being produced right under your ear. This is an especially good trick to use in the concert hall when you are adjusting to the acoustics. From my current teacher, Keng-Yuen Tseng.