My day job is with a company called SonoPlot, Inc., which I co-founded. SonoPlot manufactures and sells robotic systems for the printed electronics and biological research markets. Among other things, I write our control software in Cocoa.
I do Mac and iOS development on the side in my one-man company Sunset Lake Software, with a particular focus on the iPhone and iPad. I provide the source code for my Molecules iOS application under the BSD license, but I do sell an application called Pi Cubed as well. I'm the author of an open source iOS framework called GPUImage which lets you perform GPU-accelerated filtering of images and video.
I also taught a course on advanced iPhone development at the Madison Area Technical College, for which the fall and spring semesters' videos can be found on iTunes U (this has also been made into a full course for the new iTunes U app). Class notes for this course (with links to sample code and other resources) can be downloaded here in VoodooPad format.
Like everyone else, I'm also on Twitter.