EDIT: I should add that this is one of the main reasons I got started in the field of online backups: There were lots of online backup solutions available, but I wasn't impressed with their security -- and due to being FreeBSD Security Officer, I tend to have sensitive information (e.g., about unannounced security vulnerabilities in OpenSSL/BIND/Sendmail/Apache/etc), making it absolutely essential that my backups be secure.
http://www.welton.it/freesoftware/
And lots of little bits and pieces here and there.
My friends call it Ninja Hacking.
And I'm releasing an open-source image archiving app soon.
I'll admit, I'd love to contribute to a larger open-source project but I feel intimidated at times. Sometimes I'm not sure I have anything to bring to the table for such projects ... considering the talent that already works on them.
Also, I might start writing a FOSS app of my own in the future. It's just an itch I want to scratch.
I can contribute to FOSS because I'm still in college. I guess people with jobs or startups might not have enough time for, um, "extra-curricular" activities.
Open-source system automation for the cloud.
I've also contributed extremely insignificant patches to django and turbogears.
I'm not a startup hacker though...
i've contributed patches to a number of other small projects that i don't keep track of.