Sweet Acacia
(Acacia farnesiana)
I won this tree in a raffle at our bonsai club meeting bonsai club meeting in August 2005! In the evenings, these very delicate leaves all close up, which is pretty interesting. I understand this tree gets yellow, puff-like flowers, too!
Here's some detail of the leaves closed up at night:
This is what it looked like after a dramatic pruning on August 26, 2005:
The Sweet Acacia gallery can be found here.