Yo dj baniak...
Methinks that the drum you're thinking about (bawoomp) is the udu, I mentioned it in another post. It's an instrument whose origins reside in Nigeria... it's basically a modified clay pot, with an extra hole in the middle. They don't lend themselves well to drum circles, though, because they're so quiet. To clarify, the doumbek is gourd-shaped, like the djembe, but has a flat top head, and is traditionally played underneath the arm of the performer.
As far as drum circles go... yes, there are dirty smelly hippies... that's not just a stereotype... but you're right, nothing beats the communal experience. Generally, drum circles will evolve from one beat, started by one performer, and end up being a completely different entity, as more people add and subtract their musical input. Depending on how many people attend, and how hardcore they are, it might just be a constant, ever-evolving rhythm that lasts for hours.
To improve your hand-drum proficiency (this is an extreme generalization) the key is creativity and a sense of rhythm. Usually, in local drum circles, no one cares about your technique; it's all about what you can contribute to the group. You can practice for hours getting your strokes to a lighting fast pace, but what good is that when you're jamming with friends in the circle? Listen to all types of rhythm-based music, whether that be hiphop, classical, or post-rock, whatever moves you, and just transfer that feeling to your drum. You'll be a master of styles in no time
The_Kid