Disclaimer: I'm a linux guy, and have stayed away from Macs like the plague.
Aside from that, it seems to me that you have two options:
Either upgrade your rig although that seems unlikely that you could upgrade that machine, considering it's Macintosh, and they probably discontinued parts for it years ago. However, you might be able to find more ram via a model bought online and subsequently gutted, but that's more risky than sporting a mullet. (Unless in the unlikely event, you can use parts from other models or their is an illegal third party company that is selling parts.)
Your second option is to suffer it out: From what you've described, it seems exactly like the behavior you would expect from browsers that aren't HTML 3, 4 or 5 compatible, because they don't conform to the standards it makes things generally glitchy and a pain to work with. (Hence the need for a script monkey.) In addition to your low system resources, the browser is going to have to pass a (relatively) large amount of data through a small pipe with rust and holes in the side, problems are going to be a fact of life unfortunately.
However, you might be able to use a resource lean browser such as iCab and that could improve your performance, but I doubt it would be anything super dramatic. I know of a large amount of browsers are based around this concept (nerds don't like to throw anything away.) you would just have to do some googling to determine what would be best for your particular software/hardware situation.
If I may ask, where in the world did you find this computer? Also, is accessing these forums a chore? Because I find the wait time intolerable on a high end system with a 10 mbit connection.
