I've been working on developing a three finger pizzicato technique. NHOP had a great technique as can be seen in this video.
I've been trying to develop this skill with some success, but wanted to develop some more refined techniques and a less ad hoc sense of when this type of playing is best (read: when to use my ring finger for agility and speed). The problem, as I see it, has been on developing my ring finger to play more than just ornaments on the G-string.
I came across Sigi Busch's Jazz Bass Compendium and it has some exercises to get one thinking about how to incorporate your ring-finger (denoted with an "a" in the exercises) into your playing. I have found these exercises useful in getting started. The next step is to develop your own exercises, scales, etc which incorporate your ring finger in a systematic way. Here are his exercises: