There are plenty of fun and educational sites on the Internet for kids. One of the more famous is perhaps Starfall.com, which teaches kids to read and write using phonics.
Other great sites that your child might want to try out include Sheppard Software, a site with many fun online activites for Kindergarten, and SproutOnline, a PBS website with games featuring characters from the most popular PBS TV shows.
If you kids prefer watching videos to playing online games, check out this list of websites that are like Youtube for kids.
For kids learning their multiplication tables, Timez Attack is a fun arcade game to download and play. Math Playground is another interesting site with lots of interactive math games. Of you could, just for fun, try out some IQ test for kids.
For kids who want to learn real, fast QWERTY typing, you can download some of the best typing tutors here.