As Jorden said, Open source and free software can often be just as good as the commercial software that has the same purpose.
Open software comes in many forms for many different operating systems and even come in the form of many different operating systems, some examples are FreeBSD and Fedora, both are free operating systems. You also have general use software like Synfig which is a 3d and 2d animation program and Scribus (similar to PageMaker, publishing software)
But there is also free software that allow web servers to be run, some examples are the Apache software foundation and Xerver free web server. You can even add PHP and CGI to your server for free by downloading the PHP software from php.net!
Aside from this there is also web based php-installed software that usually require PHP and MySQL databases, some examples are content management systems such as Drupal and Joomla which come in very handy for business interior communication, there is also phpBB which is a free forum software, there is also helpdesk softwarem. Many free web hosts have these ready to install with one click now (usually powered by Layered Panel) an example is freehostingnow and freeweb7.
Open Source software is certainly the way forward and you can get involved in developing it!
A large list of open source software can be found here:
http://en.wikipedia.org/wiki/Open_source_software