Motocross Madness 2 is also still up: http://www.microsoft.com/games/motocross2/ And this list wouldn't be complete without Midtown Madness (1?) http://www.microsoft.com/games/midtown/ [edit] I'm sure you can find a bunch of others by browsing through the wayback machine ( http://web.archive.org/web/19980214201021/http://microsoft.c... ), like http://www.microsoft.com/games/outwars/
Motocross Madness and Midtown Madness were both such fundamental pieces of my childhood. I wish I could convey the amount of nostalgia I have. Motocross Madness was the first time I actively tried to use a computer to 'do' something. I had to program my own tracks, and it was insanely hard at the time, but god were those the glory days.
I'm with you that game was amazing. The track designer was such fun. Really wish they would have continued the series. The track designer was really easy to learn I feel compared to the current modding tools that come with games. And it had enough stuff to keep me for a long while. Must have played that game for a few years.