We developed SourceGuardian.com as a side project from my main company (Inovica.com) as we had a need for PHP encryption and were not prepared to pay the thousands of dollars that one company was charging at the time. We developed it for our own sites and then packaged it up to sell it to others. We had some teething problems with the earlier versions, but we're still here a number of years later. It's still a side project (and we have a few of them!!) but it brings in revenues of around $70,000+ a year. There is a team of three people though that worked on this side project and which share on this.

We also run:

www.europeantenders.com - Around $20,000 a year

www.ukscrap.com. This did amazingly well when scrap values were high (we were doing around $2000 a day) but they have become quite low at the moment so its only just covering its costs.

Hope the above helps. Happy to provide more info or help to anyone who wants it