GrassrootsMappingThis is very similar to Balloon Aerial Photography, but with kites! Kite-specific information is here, but for the rectifying process (to stretch the photographs onto a geographic grid), see Map Warper.
You can buy a kite (a soft kite for portability… no rods!) or build one yourself.
Build a Box Kite: Instructables guide to buildilng a box kite - this one requires a bunch of 36 inch long, 1/4 inch wide wooden dowels, and some plastic tarp and string. It flies in 8-20mph wind and not more than 25mph wind. This is a nice simple kite for building with a group of kids and minimal materials.
Look at some very nice kites for sale here, starting at $25: http://www.foreverflying.com/sutton.html
Instructable guide for making kit string winder - really important… knotted kite string is the worst!!