Talk to people around you (barber, barista, waiter, friends and family, etc) about the technology that they use. (smartphone, facebook, etc) The conversation almost always turns to complaining about how they wish things would work. Those are your problems to solve.

I look to my daily life and those around me. I am fortunate enough to work in a co-working space (Affinity Lab in DC) that isn't only filled with technology companies. It's a diverse group of people covering all sorts of different fields from technology, to media, to accounting, marketing, pr, products, charities, etc. We talk, a lot. There are tons of problems everyone faces, some are common, some aren't. But you get inspiration. Maybe some are common among different areas, some might be common among the same niche. But having access to discuss your issues and other people's issues really helps me see the problems people encounter. Sometimes it's about sharing different solutions because they are solved (or there is an easier way, not perfect, but easier), sometimes you need to come up with something.

tl;dr: talk to people, it helps if you're part of a diverse community of people.

Why not build a site where people can post problems solvable via software?

with a slightly different approach, we've built a website so people can publish project ideas. since it's only a prototype, it's a bit messy right now but we'll release a new version at the end of the summer, with a specific category for weekend projects. http://www.gullibear.com/

That's (a bit far from intuitive but) gorgeous.

I recommend listening to the Mixergy interview with Sam Ovens.

Thanks guys. I guess I need to be more aware/pro-active with my surroundings to find the problems.