I know I -- and I assume many others -- would be interested to hear about HNers' most successful side projects.<p>Wherein side project is defined as something started by you -- with or without others' help -- on the side of a full-time dayjob that turns/turned a decent profit, was sold for a decent amount or has considerable uptake and a bright future.<p>I'll go first. In 2005 I started a designer community event called CSS Reboot that, in its 1 1/2 years under my ownership, made $5,000 in ad sales. Fall 2006 I then sold it for $10,000.
Many years ago, I developed an extension named AdBlock for the Phoenix browser, instead of studying for an exam.<p>I unfortunately haven't taken part in its development for a long time, but I still get a small kick out of seeing it mentioned around the net, and I love seeing how the project has been adopted by people far more disciplined than me.<p>Some other side-projects, which achieved less renown, can be seen on my homepage.
My company, LightSail Energy, started as a simple question: whether enough power could be recovered froma garage roof to power a daily commute. It's now a small startup that's raised money from a top VC, we have a working prototype and excellent forward momentum. :-)
All "side" businesses, concurrent with growing up, education, sports, jobs, etc.<p>Age 6: Ran a neighborhood service "Rent a Kid for Odd Jobs" ($25)<p>Age 10: Made wax candles in my backyard and sold them to a Mom & Pop store ($100)<p>Age 12: Grew tons of plants at home and sold them to a nursery ($400)<p>Age 18: Created basic websites (HTML, CGI/Perl, PHP) for businesses ($10,000)<p>Age 22: (while in grad school) Coached Tennis ($1000)<p>Age 29: (Current) Looking to buy and sell cars, i.e. auto-brokering. ($0 so far)
I have an outsourcing business that brings in about $3000/mo profit. Clients include web design/development companies, and small businesses who need "intern" work done. All work is done in Cebu, Philippines.<p>I had a comparison shopping site with affiliate links back in college (1999-2000) that I started with 3 friends. We pocketed about $1000/mo each until mysimon.com came along.
Doesn't exactly fit your criteria in terms generating revenue, but I wrote a plugin for TiddlyWiki (<a href="http://www.tiddlywiki.com/" rel="nofollow">http://www.tiddlywiki.com/</a>) that allows you to store your address book inside a TiddlyWiki file. It includes import and export, and since TiddlyWiki is JavaScript based you can fully script your address book to your liking. It's called TiddlyWiki Address Book (i.e. twab, <a href="http://www.tiddly-twab.com/" rel="nofollow">http://www.tiddly-twab.com/</a>). It's fairly popular among those who use TiddlyWiki and more importantly is something I'm proud of for a number of reasons.
Back in '87, I wrote a little Mac shareware INIT that grossed around 20K over a few years. Almost 4K registered users (counting a BigCo license for almost 3K seats @ ~$1/seat).<p>It made a MacUser cover story (along with about 50 other utilities).