Well, it isn't really all that satisfying, but I've taken to tutoring, specifically SAT tutoring. This has good points ($40-$50 / hour, not very difficult) and it has bad points (relatively mindless, highly repetitive, can be a lot of driving). Still, it is a flexible solution to a very stressful problem.

Well you've got the www.rentacoder.com type sites. www.odesk.com is another. And then you've got whatever you can dig up on your own through independent consulting. Just be sure not to break any agreements with the startup with respect to IP, competition, etc.

And then there's always waiting tables. A bit of a shot to the ego perhaps, but that'd be a good break from coding perhaps. If it's good enough for every budding actor/screenwriter/director in LA... :)

My cofounder works this way and I have all the respect for him for being able to carry this out without it having an impact on our development.

Still you have to be very careful it does not take your focus away at any point. My partner had freelanced before so he knew what kind of projects to take and not take. Best projects are those that pay for some straightforward coding without much mental work.

A while ago, I remember reading on Emanuel Derman's blog (http://www.wilmott.com/blogs/eman/) a comment along the lines of "Time and the right to choose have value".

So while I'm sure you can find some job to pay the bills, consider how much time (and in what state mentally/physically) it will leave you to focus on your startup.

Personally, if I was ever in this situation I think I'd go for a mindless job like becoming a Starbucks barista or something. I find it's harder to have good ideas at home after doing something that involves thinking all day.