Ok, this is how I started.
Back in 1999, I was a newbie on the local lug and was learning perl. There were people of all skill levels on the lug and one of the non-technical members asked how he could find out the type of web server running on a host.
I replied telling him how to telnet to port 80 and do a GET, but then realised that that was a bit to technical for him, so told him that if he waited 30 minutes, I'd write a script that would do it for him.
I got a chance to use my new found perlipc skills, and released my first GPLed application. The app grew over the next few months based on one-off patches that other people sent me, each for a need that they had.
Now, this was my first solo project. About a year later, I joined the "everybuddy" project. I was looking for an opensource instant messenger on linux, and found everybuddy. Downloaded it, built it and started using it. A couple of days later, I noticed a few bugs with the Yahoo! Messenger code, so I started debugging and fixed a few. I mailed in patches. I had to bug the developers a bit to get the patches accepted.
Finally I asked the project maintainer (Rob Lazzurs) who the owner of the Yahoo! code was so that I could mail that person directly. He replied immediately "as of now, you are". A few minutes later I had commit access and was a full developer on the project. A day later Yahoo! changed their authentication protocol and I had my hands full. 3 years later Yahoo! hired me.