Volunteering in Arusha (or other areas around Kilimanjaro)

Climbing Mt. Kilimanjaro is a fantastic experience, but I was considering spending some time either before or after the climb doing some volunteer work in one of the villages around the mountain. Can anyone recommend any short term volunteer opportunities? Has anyone done something like this before? Any suggestions, regardless of scope, are welcome. (My particular interest would be in the fields of engineering or health.)

I vaguely recall one group, based out of Ohio, that does volunteer work in Arusha or Moshi. If memory serves me right, this group was fairly small and organized volunteer work anywhere from one week on up. The gal that founded the group moved to Africa a little over a year ago and currently runs operations there now. If you happen to know the name of this group, or any other small group, please do let me know.

I can be reached by email at kilimanjaro2009@gmail.com

Thanks!
-d