I've started 2.
One isn't doing as well as we'd hoped because frankly there are just so many alternatives out there and to compete I'd need to invest about $3000 per month in marketing alone. Our costs are minimum since we're 100% intangible and hosting on a DigitalOcean.
The other is non-money making except for advertising on the site. We're ranked #2 in the world in our niche and we could easily swipe #1 but I just don't have the time to implement the necessary features. http://smitecamp.com/ - We've seen traffic increase by about 6% week by week since launch, and Google ranks us favorably because we're a no-bullshit website.
My brother and I are working on #3 - again: 100% focus on advertising for steady revenue. This one I feel we'll hit paydirt. But we'll see.