Problem-Based Learning is not just handing out your typical story problem from the back of your book (though they may have good starters!), it is about presenting an issue to your class, using protocols such as "I Notice, I Wonder" to start investigating the problem at hand, and then working through the Problem Solving Process to generate one or multiple solutions. Problem-Based Learning doesn't just end when one solution has been found; as the problems are generally open-to-interpretation and solutions are based off of one persons problem-solving process, it is quite possible that a problem used in Problem-Based learning could have more than one solution or more than one way to getting to the same solution. The fascinating part appears to be watching students discover why.
Problem-Based learning evokes many of the same things I want my students to get from Project-based learning: an inquisitive mind, a productive-struggle to learn, critical thinking and analysis of information. As such, it seems to be the perfect complement to a Project-Based Learning school.
For more information on the difference between Project-Based Learning and Problem-Based learning, check out bie's article: Project-Based Learning vs. Problem-Based Learning vs XBL
Problem-Based Learning Resources:
|Math Forum @ Drexel: Problems of the Week|
|Emergent Math CCSS PrBL Mapping|
|Mathematics Assessment Project|
Other Awesome Websites to Support PrBL:
Dan Meyer's Three Act Tasks