Thanks all. I've been paying wedding assistants in the $200 range for about 6 hours (sometimes more) of help. One of them brings his own equipment. The others I use shoot with my equipment. They don't do any post-production, they just shoot and I take the images.
From those of you who did quote some prices, it sounds like we're all in the same ballpark. Good. I think a couple hundred bucks is a small price to pay to have someone there covering the important parts of the day from a second angle, just for insurance if nothing else. My assistants aren't super-amazing shooters, but if they were they'd probably have their own business. On a wedding, an assistant might end up shooting 300-400 images. If 50 or so of these end up being good enough make it to the final cut, then I think it's well worth the price.
And it sure helps to have another pack mule (besides myself) to lug the equipment around all day.