I know that many of the Wolf spiders carry their spiderlings on their back, so that's what I would say your spider is. They can also tend to get quite large. Your location would be helpful in pin pointing a good identification.

We're in central Virginia. I believe that the spider I saw last fall was a Wolf spider, but this one did not seem to be furry like a wolf. Or, do they go through a "hairless" stage? My spider book just says that some species carry their young on their backs, but does not elaborate as to which ones.

Not all wolf species are hairy. I'd also guess some sort of wolf

:)