One of the first apps I installed on my new MacBook was OpenOffice. I love it; it's free, it gives me every bit of functionality I need for a home office user.
However, I was incredibly dismayed to find out that I needed to install X11 just to run it; it's not using OSX natively.
But somehow I discovered NeoOffice, an Open Source port of OpenOffice. It is free as well, but it has integrated dozens of native Mac features. It can run without the use of X11. I've been using it for a little while, and I love it!