I wrote 10MinuteMail.com in order to teach myself the JBoss Seam framework. I hadn't looked to see if there were other sites doing the same thing (there were),

I wrote 10MinuteMail.com in order to teach myself the JBoss Seam framework. I hadn't looked to see if there were other sites doing the same thing (there were), with more features (there were), etc... and never intended to make any money with it. It got pretty popular and I make a bit on Google Ads. Not enough to retire on or anything, but it makes low five figures annually.