There's a MacOS X version which you can grab at VersionTracker.com. It should run fine on an iBook 500, since my 400 MHz Blue and White G3 play it flawlessly. I should note that I haven't tried it since I upgraded to 10.1, but I haven't heard of any problems, either.
amo: I'm running a SE graphite iBook and The Sims runs awsome under 10.1! I don't know if you really want this game though...since you can get tired of it very fast. But it runs smooth if your sure you want it!