I'm afraid I'd have to disagree with wrens. Wrens have pretty short tails, both the carolina and house wren are pretty much brown. House wrens build the ugliest, most uncomfortable nest I've ever seen next to dove nests. The few carolina nests I've seen have been low and pretty well hidden, and their eggs are pinkish in color.
I think someone posted a few pics of pewee nests not too long ago. Seems to me they used moss and stuff that you're describing.
Don't cry because it's over, smile because you were there.