and my kids had a blast. 2 things that really stick out in my mind I did were:
the landform cookies. i know, i know....crazy nutrition things, BUT, if they take them home and dont eat them at school, I got around it. meh.
I bought sugar cookies (plains), snocaps (mountains w/ snow), yellow decorating sugar (desert), green deco sugar crystals (grassy plain), blue squirt icing (rivers/lakes/pond, etc) and for the valley i had them make a thumb print in them. I wish i had pics but they turned out really great and the kids would go around showing what eat part was to other kids.
the other thing I did was to get alot of images of different landforms. I made a powerpoint slide show of these and had a game with those little bells from walmart you ding. 2 teams and whoever rang in first with teh correct identif. of what landform they were looking at won (they won like, extra library time).
If you do someting for deserts, it may be hard to find this time of year in stores, but when i talked about cold (tundra) and hot deserts-i bought some of that fake snow that you add water to, put lamitated prints of things that would live in either desert, had the kids dig thru it and and match which plants/animals would live where....
I hope this helps!