I am The Oatmeal. AMA
I'm the guy who runs The Oatmeal. The Oatmeal is a one man operation; I write, draw, code, market, and maintain everything myself.
I use Adobe Fireworks to draw everything, and the site runs on CakePHP, mysql, and lighttpd. I use a mac and I draw with a mouse. I have a tablet but I hate it. I also suck horribly with Photoshop.
I recently did an interview on TheDesignZine which answers a lot of questions in regards to workflow and where I get my inspiration from, and there's also a bit more detail about me on my rather outdated about page.