"Best" varies wildly from market to market, but if I had to pick, I'd start with folks whose job is creating and improving landing pages:

http://landerapp.com/

http://unbounce.com/

http://www.crazyegg.com/

https://mixpanel.com/

https://www.kissmetrics.com/

http://copyhackers.com/

This short list already covers a lot of different styles. Some may even look a bit dated, but you can be sure they are converting very well, because that's what they are optimizing for.