This topic has come up in conversations at my school and perhaps at yours as well. There are many people who believe that it is only necessary to be able to hunt and peck on a keyboard, just as there are many who believe that being able to print is sufficient. I'm not really going to get into that debate, although I will suggest that at some points students will be in high school or college, and the quicker they can type their 5-page papers, the happier they'll be. I'll also say that I absolutely hated typing class in both 8th grade and business college.
Luckily, there are plenty of web sites that teach typing, and I'm sure most of them try to make it fun. A simple search of keyboarding for kids brings up a list of web sites. My own 4th grade students liked Dance Mat Typing, but it requires flash and is really more suited for children who are at home, as opposed to those competing with an entire school for access to limited computer bandwidth. The site is produced by BBC, but my students enjoyed listening to the accent.
Learning Games for Kids has a number of different keyboarding games. For example, Homekey Kenneys has a sort of whack-a-mole concept in which the player types a homerow key to eliminate the little guys.
I have only looked for tutorials with QWERTY keyboards, but I'm sure there must be other types out there as well.
If you have another keyboarding site you like, please leave a note in the comments! Thanks!