This slime mold will develop further 'til it looks like a cluster of fuzzy brown cylinders attached to the wood by hair-thin stems.
I have no idea what this is, but I'm guessing some sort of fungus. We have had a lot of rain lately and I found this on the door to my garden shed.
Stemonitis is a distinctive genus of slime moulds found throughout the world (except Antarctica). They are characterised by the tall brown sporangia, supported on slender stalks, which grow in clusters on rotting wood. Identification within the genus is difficult, and can only be performed with confidence using a microscope.