Are there any office suites available that I can use legally without having to pay?

Although there are quite a number of options available, two of them demands a special mention:

OpenOffice.org
This is definitely the heavy-hitter of the bunch — it's a complete office suite that includes database, spreadsheet, drawing, presentation, maths and writing applications. And the best of it all is that it's completely free and open-source software.

Visit OpenOffice.org for more information.

Google Docs & Spreadsheets
The biggest advantage of Google's offering is that not only is it free, you also don't need to download and install anything on your computer. Apart from the fact that this means more disc space for other applications, it also means super portability, as you store your files on their server, from which it can be accessed from any computer. Just log-in and there you go.

Visit docs.google.com for more information.