The Blucig and the V2 are probably the most popular next to the EGO which is highly recommended as a step up from the smaller cigarette size style of ecig. I've been using an EGO now for almost a week and already looking for a larger system that runs at a higher voltage and with a superior battery life.
If anyone is a smoker of a pack or more of cigarettes a day I strongly suggest you go with an APV that uses a 18650 battery or comparable. I go through about 3-4 battery changes per day with the 650mah battery that came with my kit.
The Silver Bullet is the most popular APV and has been around for a long time.
http://altsmoke.com/starterkit/silverbulletusa.html
There is a link at the bottom of that website for the affiliate program.