Pages is not free so as was mentioned earlier in this thread, unless you still have some form of trial period left, you'll have to buy a license to use it. The iWork suite is actually a good suite that shows a lot of potential.
OpenOffice was suggested in this thread. That's a terrific product and unbelievably it remains free. Yes, it is quite slow to load at first but once it gets going it's fine. That, by the way, is a problem with the product across every platform I've used it on -- Sun Solaris, MS Windows, Mandrake Linux, and Mac OS X. One slight modification I'll make to that recommendation: For OS X choose the NeoOffice distribution of OpenOffice. It's still free but is more Mac oriented and seems to run slightly better. It is the same product, just slightly tweaked, and still free.
Now, depending on what you need, one product may in fact be a better fit than another. I'll mention a few words on OpenOffice (NeoOffice), MS Office, and iWork.
If you require solid functionality for free, choose NeoOffice (OpenOffice for the Mac)
If you use spreadsheets a lot, MS Office is probably a better fit.
If you add art to documents a lot, Pages is probably a better fit. It makes it very simple to position graphics relative to the left, center, or right of the page and relative to other objects on the page.
If you absolutely require the ability to open documents created in Office apps on your Mac, choose MS Office or OpenOffice (NeoOffice). Pages drops a lot of Word formatting although it will still open the .doc files. OpenOffice does a surprisingly good job at reading and writing the .doc and .xls formats used by MS Office.
I have anti-Microsoft tendencies and was very reluctant to even consider MS Office. I'm pretty sure there are threads in this forum in which I've slammed MS Office for one reason or another. Well.... I broke down and tried it. MS Office 2004 for the Mac is by far the best implementation of MS Office I've ever used. FAR superior to the varieties that run on Windows. The icons aren't quite what I would consider intuitive but I'm sure they'll be simple to learn.
If you have a nearby Apple Store, head in there and ask if you can spend some time on their computers using MS Office and/or iWork. Hopefully they'll have both.