Other Internet utilities
Quite a few of the traditional Internet utilities -- Ping, Telnet, FTP, Traceroute -- are built into Windows, although many people are unaware of it. To access those functions, pull up a command prompt and type them in with the host name you're trying to reach. Ping and Traceroute are network debugging utilities. Telnet allows you to operate a remote computer as though you were typing into a terminal connected directly to it. FTP stands for File Transfer Protocol, and its functionality is built into your Web browser. Nonetheless, there are times when you'll need to be able to use FTP, and times when you'll find it handy -- for example, if a connection keeps dropping, because unlike the Web protocol HTTP, FTP can resume a download partway through.
Besides those, you may like an IRC client for chatting to other people around the world, instant messaging software, video conferencing software, IP telephony software and perhaps blogging software. The main instant messaging services -- ICQ, AIM, Yahoo! Messenger, and MSN Messenger -- are all free. There are free IRC clients, but the one most common among Windows users is mIRC, which will continue to work if you haven't paid for it, but properly costs $20 (~AU$30).
Social responsibility
Finally, while you're setting up your low-cost system, consider donating your spare computer cycles to one of the several distributed computing projects around the Internet -- SETI@Home, cryptanalysis, or folding proteins.
