The iBooks ship with Appleworks included, but the Powerbooks do not. It is a $79 purchase from Apple. You do have TextEdit, which will work with plain ASCII text or RTF formatted text.

There are also free options available - OpenOffice for one. AbiWord will run in Apple's X11 and can be installed via the FINK package management system. OS X can also run LaTex editors like Lyx (Lyx is actually available as a native carbon app). Check out the editors and word proccessors available at versiontracker.com and macupdate.com

Just some links to get you going:

OpenOffice and the OS X OpenOffice page (note they mention XFree86 as required, but Apple's own X11 works fine).

The Lyx for Aqua page

The AbiWord home page, and FINK for installing it (you'll also need X11)

TextEdit. It's sort of a cross between WordPad and NotePad on Windows.

AppleWorks comes on iMacs, eMac, and iBooks. TextEdit comes with every Mac.

If you're a college student, I highly recommend getting Microsoft Office for Mac with education discount for a really low price from Apple's store.

I've always just gone with MS Office. The education edition (avail to everyone) is $150, but you get Word, PPT, Excel and Entourage, plus guaranteed compatibility.