There's actually quite a large number of satellites in polar orbits, for various reasons.

I don't understand all the orbital mechanics for knowing when something's going to be visibile from a particular location, other than the obvious (sun has to be able to hit it while it's dark where you are). As one example, the Gravity Probe B satellite was in an orbit where it was never visible, synchronized somehow with the sun. Bigelow's Genesis balloon is in some crappy orbit where it shows up in the middle of the night at magnitude 4 or 5.

On a good clear night, after sunset, you can often spot several orbiting objects going in various directions. Space junk is often rotating, which makes it slowly dim and brighten as it goes over.