Actually, I'm going to dissent and say I'm not wild about the Cappuccino logo: it's too complex. Look at the small version:

http://cappuccino.org/images/cappuccino-small.png

It loses any sense of what it is, unless you already know. The larger version on the site is quite pretty, but I'm just not sure it works great as a logo. Logos should still be very clear and recognizable even when degraded a lot (size, lack of colors, etc...).

the cappuccino one fails all of my criteria for being a good logo also. nice graphic but not a logo or an icon at the size it is used at.