Kermit turned me on to this a month or so ago, and it's definitely been good to know. Have you ever seen those little strips in the street right before a traffic light?
I had always thought they were weight sensors (and thus useless to bikes) but as it turns out, they're inductive loops - little metal strips that can detect when metal is above 'em, and then trigger the light to change. So if you can aim right for 'em, you should be able to set it off with your bike rim! Some of 'em are easier than others, but I've had particular success with the light at Midland and Highland, which is nice since it's on my commute.