my only problem with free lumber is either where to store it or how to say no to more
What a terrible problem to have!
Nice ideas for sources, will have to keep them in mind. Free lumber around here goes *fast*; I don't usually bother when I see it posted on craigslist etc, because it will almost always be gone before I can arrive, even if it's just 20 mins away.
My favored lumber yard has a scrap bin you can loot... but I've never seen any decent wood in it. We're talking nothing over 18" usable length...
Other than for making compost bins, I have never understood the fascination with taking apart pallets for the wood because better scrap wood seem so common.
I'm not a big fan of taking apart pallets for the lumber outside of special circumstances, but there's just so much beyond compost bins that can be done with them! Within the couple months I've used pallets to make 5 tables and a raised garden bed; none of them were disassembled, some were trimmed with a hackzall. Benches, fences, and crude animal shelters are also easy builds.
(As far as special cases go... I've scored some lovely 8' full dimension 4x4 posts out of pallets... no idea what they were carrying, but it must have been heavy as hell!)