XUU is a solid option if you're looking for a Canadian traded ETF that has exposure to the S&P 500.
Keep in mind, XUU is subject to withholding taxes even inside of an RRSP. The tax issues are a little complex with it as it holds underlying US ETFs. It jumps the overall fees of that ETF up to the 0.31% range.
There's also the option of using Norberts Gambit and actually getting USD to buy a US listed ETF in your RRSP. This is all personal preference. Some choose to stick with Canadian listed products only, while others choose to get some USD and buy US listed stocks/products.