Another game that gets top marks for originality is Sim Taxi - where you have to quickly find the passengers and take them to their destination as fast as possible. Of all the current online games this is perhaps the most original, in which each "course" is different, but set in the same environment. You never know who will pick next or where you are going, you frantic race against time and evil to want to stop.
Racing Clock is an important attribute of successful racing games. Often, the clock is your life - you have to get to a certain point replacement within a specified period to be sure before moving onto the next level. Old racing games like Outrun used this excellent device, so you get to certain checkpoints in a race to gain the ability to carry the line. Some of the most entertaining racing games online do the same thing.
Of course, there have to be cars that race - or at least not normal! Dodgem racing is fun, and there are plenty of bike racing games out there for the petrol head who prefer two wheels to four. Dirt Bike 2, Bike Mania on Ice and Dare Devil, are outstanding examples of online games that offer a motorcycle course.