Now, again, I've never had much issue with less-than-robust RAM, but it is an issue that I have thought about from time to time. My system comes with two DIMM sockets, one of which was populated with the 512mb board. According to the specs, the system will take up to 2gb of RAM, so I went looking for some "older" (PC2100 DDR 266mhz) memory, and found one place (American Design Components) that had an appropriate 1gb unit for only $74.00 (with free shipping). While I don't exactly have "seventy five bucks to spare" in the grand scheme of things, I did have $75.00 sitting in an envelope from cashing a birthday check from the in-laws last fall. Given that the figures matched up so well, I decided that (rather that "fritter away" said cash on bus fares and burgers), I'd make the grand sweeping determination that they had bought me an extra gig of RAM for my birthday (if a bit retroactively)!
At least if tripling my RAM doesn't fix the problem with SecondLife (and you know how pissed off I'll be if it doesn't), I'll be left with a far happier computer when playing with large graphic files, etc., so it's not exactly "good money after bad".