What can I say? Snap Circuits by Elenco Electronics are awsome! They offer kits from very basic (Snap Circuits Jr...which my son started with) to advanced (Snap Circuits Extreme....which offers solar, electromagnetism, computer interfacing, etc for $129).
As I said, my son started with the most basic "Jr." kit this past Christmas. And loved it (see the review). So, for his birthday his grandparents bought him the upgrade package so that he now has the equivelent of the "Electronic Snap Circuits" kit.
The upgrade kit came with 30 new parts for him to play around with including an am radio component, more lights, transistors, integrated circuits, resistors, and much more :0) Very cool and I'm not even into electronics!
My 9 year old opened his present at the party and his 15 year old brother could not wait to get his hands on it....in fact, he snuck it off the table, opened it and riffled through it like a little kid with candy, LOL. Once we got home, my 9 year old broke it out and began to play (he chose this over Speed Racer legos and a very cool remote control car). He played with it until the batteries ran out!
With the Jr kit, there is a book of 102 experiments. The upgrade comes with yet another color printed manual for over 200 MORE experiements to snap together including: Radio Music Alarm, Standard Transistor Circuit, Race Car Engine, Finger Touch Lamp, Door Bell, etc. Each project is SHOWN in color so that the child can see what it should look like, as well as a small paragraph of exactly what piece to snap where.
PROS: It is educational, inexpensive, encourages indepenent play, builds confidence and self esteem. And best of all these peices can be snapped together in any which way and they are not limited to the projects the book shows. In fact, my son gets the most enjoyment out of doing his OWN projects. And another cool fact is that if you make a NEW project with the peices you can send in the info and it might be included in their next book!
CONS: Really non other than the batteries it uses :0)