Speedplay makes clipless pedals
and mountain bike
The road pedals are sometimes called "lollipops", because, well, they look like lollipops. Advantages are that they are light, have high cornering clearance, have good float, can be engaged from either side and most people find them relatively easy to engage and disengage. Disadvantages are that some people have reported getting hot foot with these pedals.
The mountain bike pedals are also double sided, but look like a solid plastic oval with a metal ring in the middle. Advantages are that they don't get clogged with mud, are double sided, and they are mechanically very simple. Disadvantages are that some people report false "lock ins", and the cleats are not as durable (and relatively expensive).