There is a large amount of free software currently available on Internet. There is an interesting article called The Cathedral and the Bazaar by Eric Raymond that expounds the advantages of openly developed software.
Much of Internet was developed over the years from software descended from AT&T / BSD Unix. Though Linux is not from that stable, it was specifically designed to be compatible with software developed for those platforms.
The Netscape browser runs on this platform, and it has recently been announced that the next version, Netscape 5.0, will be released with source to better take advantage of the free software model.
Linux runs on PC class machines, currently 386 and above, and also on a wide variey of other computers, like Macintosh. It can even share disk space with Windows or Macintosh operating systems. In contrast to many of todays operating systems, it does not require the latest new computers to run, though it can take advantage of all the latest enhancements.