Project Car Mag had a simple DIY write-up a little while back.
The jist of it?
1. Spray Windex on tint.
2. Take black garbage bag and cut it so it's open (like down the seams), tape to window you are removing said tint from as best as possible (so as little air as possible can escape, doesn't necessarily need to be air tight though.)
3. Let the sun do the rest (or if it's cold/dark out, I imagine a hair dryer would accomplish a similar effect.)
The effect I speak of? With the garbage bag taped around the tint, the heat will cause the Windex to evaporate, thus permeating through the tint making it essentially peel right off.
I haven't done this personally, but I heard it works well and it makes sense. I was planning to do it do my ED7, but I'm lazy