Watch the 3 Note Pentatonic online guitar lesson by Richard Hallebeek from Scale Creativity Guidebook
You can also play your pentatonic scales with 3 notes per string. You probably know one or more of the 5 regular pentatonic box shapes that use two notes per string, so take one of those shapes and extend it to the next note in the scale to find the 3rd note. When you start out, it might be hard to make that stretch, but if you start around the middle section of the neck it will be more comfortable to start with. The first thing you'll notice is that if you play this scale up and down, it will give you a repetition on each string. I'll show you some ways to play around that, or the repetition might be a nice effect to use.