Honestly, I'm not much of a smoothie drinker. The "green" smoothies tend to do bad things to my digestive system.
Almond milk is very low-calorie, as well as low in carbohydrates. So it's a great base for a shake.
For chocolate, it's a good idea to stir some cocoa powder into a little almond milk until it's smooth before adding it to the smoothie mixture.
I've found that almond milk, ice, a little Splenda, some unsweetened natural, smooth peanut butter and the cocoa mixture make a very good low calorie shake that also has a fair bit of protein. It's a very filling concoction and great for breakfast, lunch or a snack. Definitely worth trying.