Awesome² 
What speakers did you use? (8ohm 0.5watt?)
How many db did you get? (It seems as loud as a smartphone on full volume)
On your schematic you didn't use any amplifier, right?
Since you nearly answered all component related questions, you should add the whole list to the first post if possible!
Thanks!
Right, no amplifier needed (although you could certainly add one if you wanted it louder and could find room for it). I don't have any equipment that would allow me to measure it in db, but it's loud enough for me. Smartphone on full volume is probably a pretty good comparison.
I used this speaker in the finished product (8 ohm, 2W):
http://www.thecustomsabershop.com/2W-28mm-Bass-Speaker-P662.aspx
During my breadboarding, I used a very cheap 8 ohm 0.5W speaker that I harvested from a toy. It worked fine, but the sound quality was pretty terrible. Really you should be able to use any 8 ohm speaker with at least a 0.5W power rating. It all depends on your budget and what kind of sound you're looking for. I'll leave that discussion to the audiophiles.