Having owned a PowerBook G4 for some time now and trying to make the best of it, I've come to gather a lot of knowledge on the web browsers you have available to you. Here's a short version:
TenFourFox is going to be your best choice for content heavy sites that use things like Flash (although you'll have to reactive the Flash plugin in the newest version of this browser). It's a PowerPC version of FireFox 17 and works great.
TenFourKit is a project that's dedicated to keeping the webkit on your computer up-to-date since support was dropped years ago. You can run it as a standalone web browser, it will come up as Safari 4 and behave entirely as such.
Camino is another FireFox based browser but it's based on FF 4 so it's growing very long in the tooth right now. It also doesn't support addons.
There's many many more but I don't have time to rewrite a large article I wrote long ago. Let me find a link to it..
Here ya go, I put a lot of work into this. I should update it... http://timemachine.myapplespace.com/profiles/blogs/web-browsing-on-ppc-has-never -been-better