While it probably is expanding foam, it does look suspiciously similar to something I saw in a horror movie once. Keep an eye on it, especially if it appears to be growing larger or if people that go into that house start turning into zombies.
(The blob I saw on TV ate people's brains and keeped getting bigger until the army had to be called in to destroy it, but even they couldn't. So, you might want to take care of the problem while it's still small.)
Last edited by Nestor_Kelebay; 05-18-2009 at 09:08 PM.