I have been picking up nxt 1.0 and the lego education 9797 sets on craigslist for no more than $125 over the last year. I have found 7 of them so far. I have picked up the older RCX lego sets for as little as $50. They have only needed a few missing pieces that have totaled about $20 on bricklink.com. The NXT kits are great for all ages. I am using them to run summer camps and help scouts get the robotics merit badge.

I second the recommendation of the OWI Robotic Arm Edge. I have used it with hundreds of students every summer most between the age of 7 and 13. It works great. If you do build it you should help them read the directions. They tend to miss little things. To save yourself from frustration later on find the baggie with only one metal pin or axle. Remove that axle and the four small tapping screws and place them in a ziplock baggie. Give the ziplock with the parts back to the builder when they have successfully reached the stage where they are building the gripper. That axle is about a mm shorter than all the others and is easy to use in one of four gearboxes that raise and rotate the arm.

So many science toys look cool in the store and suck when you actually try them out. The Air Hogs line is a great example of when function unfortunately follows form. So many of their toys look cool but have the aerodynamic qualities of a brick. This is not to say that they have not had some great products over the years. I run a science education company called Mad Science of MN so I buy and test a lot of toys for use as activities in my classes. Here are my suggestions. #1 Lego Mindstorms NXT 2.0 I have been using the mindstorms systems for many years now and they are amazing. You do need to have a minimum of computer knowledge to get them set up so the kids can use it. There are so many things you can do with these sets it is amazing. If they really like it you can get them involved with the FIRST Lego League and they can actually compete building robots. It is a bit expensive but it is worth twice the price. #2 Brain Box Electronics These are the same as the snap circuits mentioned in other posts. They are easy to assemble and the color coded directions are easy to read. This brand is a bit cheaper than the snap circuits. You can short out the batteries so you need a bit of supervision or things could get hot. http://www.amazon.com/Brain-Box-500-Electronic-Learning/dp/B000NBY318 #3 Just about anything from Stephen Spangler Science I love this guy. He knows how to make science fun. His kits often lack the flash of the junk on the shelf at Walmart but they have it where it counts. Get a geyser tube to do the diet coke and mentos fountain. Do it outdoors though or you might need a new ceiling. Check out his other kits and look at the class packs if you want to do an experiment with your kids classes. #4 The OWI Kabuto Mushi and the Robotic Arm Edge I have been using OWI robotic kits for my robotics summer camps for years now. The Kabuto Mushi would be perfect for the 9 year old. It runs around on tracks, with a gripper that can pick up and carry small objects. Best of all it is wirless IR with 8 different channels. The Edge arm is my new favorite. It is expertly designed and easy for younger kids to assemble with some adult help. Both are great parent kid projects and a lot of fun when you are done. Both of these really kick their imaginations into high gear. Check out OWIs other kits as well. Thanks Colin Mad Science of MN

My company currently runs robotic programs for this age group. With kids K though 1 we have them explore a variety of robots that we get from OWI (www.robotkitsdirect.com). We have them experiment with various transportation systems such as tracks, legs, and wheels and various sensors such as the light sensor on the spider III and Hyper Line Tracker, as well as the microphone on the RockIt robot. We use a variety of remote control robots such as the Kabuto Mushi, Soccer Jr., and Air Zinger to talk about ROV (remotely operated vehicles) We also use their robotic arm kits with a laptop interface. We link all of these to real world examples with lots of laminated pictures. For kids grades 2 through 5 you do all of that and can have a lot of fun. We have been using the mindstorms systems from LEGO for about five years. With supervision they can build a simple roaming robot with bump sensors in about two hours or less. The programing interface provided with the retail kids, not the lab view version, is very simple and linear in design. It's drag and drop programing that the kids pick up very easily. 4th and 5th graders will venture into some of the more advanced features of the programs. For our summer camps we have the 2nd through 5th graders build an OWI kit robot such as the Air Zinger, RockIt Robot, Kabuto Mushi, Robotic Arm Trainer and the Robotic Arm Edge throughout the camp. At the end of the camp they get to keep the robot they built.