I've got a

post up on GeekDad about computer games kids (and adults) can play to practice moving around in weird multi-dimensional spaces. Freelance geometer (geomatrician?) Jeff Weeks designed a 2-week-long middle-school curriculum called

Exploring the Shape of Space. Several years ago I used it to put on a 1-day

workshop for a group of elementary-school-age homeschoolers. I talked about the material (we had seen Weeks himself give a lecture at a local college), showed the video that came with the kit, and set up the different activities (making Moebius strips, playing tic-tac-toe on cylindrical boards, etc.) at stations around the meeting room so the kids could go around and try them all. Afterwards we gathered to talk about what they had found. It worked really well. The kit is still available from Amazon or the publisher, Key Press. Weeks has also written a

high school level book on the subject.