Scalextrix (or whatever) are good and all.. but they're pretty slow in comparison to some of the other things out there. I like the bigger ones (1/24th scale) which have aluminum chassis and lexan bodies. I used to race those when I was 10-12 years old. Won two championships
(even beat the older guys, too.... heh heh)
They went like stink, although the tracks were pretty much all along the same lines. Also, they aren't exactly a take-home-toy. Very few people have the space and the money for their own track, so you have to find a spot near you that has a track.
Link
That particular track only seems to have four lanes, but the place I raced at was an eight lane track.
Lots of fun