Great kid friendly site on research, interactive game board map with active links on how to do research!

Quizlet - search ready made quizzes, create your own, assign classes, a variety of activities to practice/reinforce skills

Clear, concise - lists the traits and gives active examples in a PBL unit/classroom

Assessment of student mastery of content takes many forms. This pages includes support materials for assessments that work with the Common Core State Standards and rubrics for many different assessment products. It also contains some information on the creation of rubrics and assessment in general.

Possibly a very good way to introduce the concept of project based learning.  Young children love to create/play with just a "box".

This looks like a fun activity and could be adapted for a variety of age groups. A great beginning of the school year activity.

West Virginia Dept of Educ - solid examples of PBL lessons, different curricular areas, including music

Edutopia's discussion of PBL - organized into six sections