Thomas Petra just launched a website titled Real World Math. I poked around on it a little and was impressed. He has some pretty cool ideas!
"This website is designed for educators who wish to extend the concepts of the math curriculum beyond the pages of the text. Google Earth is the dynamic tool that will be used to accomplish this. Within this site you will find lesson ideas, examples, and downloads for mathematics that embrace active learning, constructivism, and project-based learning while remaining true to the standards. The initial focus will be for grades 5 and up, but teachers of younger students may be able to find some uses or inspiration from the site. The scope of this site is mathematics, but many lessons lend themselves to interdisciplinary activities also."
Right off the bat a lesson on U-boats from WWII caught my eye. It's true that many of the lessons here can be used with more topics than math.
If you're not a math teacher, check out the lessons under "project-based learning" first. Looks great Thomas--thanks for the heads up on Classroom 2.0!