The Orb-Weaver in the window of my bathroom was fiddling around with what looked at first like a caterpillar an hour or two ago, but on closer examination the thing really didn't seem to have any critter-features -- more like just a caterpillar sized length of gunk. Just now, I noticed that it's massed the gunk together into a ball (instead of the previously elongated form), which makes it clearer that the entirety of the gunk is about 1/3 the size of the spider's abdomen.
Is that an egg-case? It doesn't look quite like what Google Image searching is turning up for egg-cases, but it could be that it has yet to wrap it in silk-down. At the moment, it pretty much looks like if someone was toying with whole wheat flour and molasses.
Monks of Doom -- "Some Facts about Spiders"