Obviously, our e-commerce sites do quite well. You can draw your own conclusions from who else is on the list
here.
My blogs do quite well, also. AdSense averages over $100/month/blog now, as does a site that we offer free e-bayish buying/selling for a particular niche. Selling links from some of those sites adds a few hundred per month.
I think the secret to really making money online is in numbers. You probably won't get to quit your dayjob with one site... it'll take multiples to get to that point.
Brian.