Common house spider (Theridion sp.)
My garage door looks pretty clean from a distance, but upon inspection it has a couple dozen, probably, of these little spiders keeping the local mosquito, gnat, and ant population down (thank you!)
A ludicrous number of species are lumped under the name “common house spider”, but these particular individuals are comb-footed or cobweb spiders in the family Theridiidae, and I’m pretty sure they’re either Theridion varians or possibly Theridion pictum, but it’s difficult to make sure.
Theridiidae are found all over the world, in North America, Europe, North Africa, Turkey, Russia, Asia, and China. Their various tiny species are brilliantly patterned and highly variable, and most merit only the tiniest of Wikipedia articles.
Adult female common house spider (Theridion sp.), prey, and spiderlings.
I can tell you that the ones on my garage are semi-social (their webs are near each other, but they don’t “visit” or share webs) and they eat smaller insects. Females have fat, plump abdomens while males are smaller, more slender, and have comparatively large “jaws”, or pedipalps.
Spiderlings (Theridion sp.) 
Adult male common house spider (Theridion sp.) 
Male (below) and female common house spider (Theridion sp.), female with egg sac. 
Adult female common house spider (Theridion sp.) with egg sac.
These photos make the spiders look huge, don’t they? These little spiders are only about 5mm long, smaller than your smallest fingernail. The babies are only barely bigger than the period at the end of this sentence. They’re so beautiful, and yet you need a camera or a magnifying glass to really see them!