My first real side-project-turned-business is/was Bugrocket (https://bugrocket.com, launched March 2011, bug tracking for small dev teams). Subscription-based and grows very slowly, it mostly hovers around $500/month in revenue. The market is just feels really small these days between Trello and GitHub Issues being decent now (in 2011 it was very lacking).
Next, my wife and I started CourseCraft (https://coursecraft.net, launched December 2012, e-course creator tools + we handle transactions for 5%-9% of sales). Since it's transaction-based it's a lot less consistent monthly, but growing faster. A typical month is $300-$400 in revenue, but it's been a lot higher (and a lot lower) here and there.
Next, my wife and I started CourseCraft (https://coursecraft.net, launched December 2012, e-course creator tools + we handle transactions for 5%-9% of sales). Since it's transaction-based it's a lot less consistent monthly, but growing faster. A typical month is $300-$400 in revenue, but it's been a lot higher (and a lot lower) here and there.