I honestly don't understand this attitude at all, assuming the people who want to "do" open source are in earnest, and not because they want to pad their CV in order to get a job completely unrelated to free software. So, assuming you really do want to do free development, why do you need help being told where to start? The typical self-motivated reason to start is because you have found open and free software that doesn't do what you want it to do, so you go ahead, and by golly, you've had enough of these blighted bugs, and you're going to make the software work for yourself (or rarely, for someone close to you that you care about).
Shopping around for something to work on without having a personal problem to solve seems like putting the cart before the horse. I assume that's not why people want to do it. They must already have a personal problem. So, what is it, what's the motivation to have a "career" in "open-source"?