Would the better question not be 'This is what I plan to do, what would be the best amount of RAM to use?' For 32Bit it will be 3Gb, I used to run 32Bit on 1Gb and for general use it was more than enough. Personally on a new build you might as well go 64Bit.
What is the max amount of Ram that 32bit Ubuntu can see?
I am building my wife a PC and I am trying to decide how much ram to buy.
We are going to be running the latest version 8.10.
It depends on the kernel configuration. Out of the box, the 32-bit version of Ubuntu can see about 3.3 GB of RAM. You can increase this to just under 64 GB of RAM by either recompiling the kernel with the PAE option enabled in the kernel config (Memory -> 64 GB) or by downloading the "bigmem" kernel (or whatever Ubuntu calls their PAE-enabled kernels) that has this already enabled.
I would also agree with the rest of the posters here and suggest that you just get the amd64 version of Ubuntu 8.10. Every new CPU except for the Atom N270 in netbooks is capable of running a 64-bit OS. The Atom N270 actually can support 64-bit operation as the other Atoms support 64-bit mode, but for some reason Intel disabled it in the N270.