Amber's Secret Cove is an etsy shop run by Barb & Jolly Blackburn (of KenzerCo/Knights of the Dinner Table fame). What I really like about the terrain items they make is the fact that most of the pieces seem a bit clunky, or "off". This adds a lot of charm to the pieces and makes them seem more realistic, at least to me.
Inked Adventures is a cool collection of hand-drawn dungeon tiles and assorted terrain pieces by Billiam Babble. Pretty cool artwork that is pretty easy to work with as well. Some of his newer designs are in black & white line art so you can easily (and cheaply) print it out at home if you don't have a great color printer.
Dyson's Doceahedron is a great little blog whose author likes to created old-school maps. The thing is, he is great at it and he pretty much releases all of these maps out into the wild. I really doubt you'll not love his site.
Dungeons & Gluesticks is a terrain building channel in the flavor of The DM's Craft, but the builds are different enough that these videos are a great addition to the other channel. There are also some more complex builds that seem easier to tackle with guidance
Grey Tower Games is yet another building channel, but most of the builds involve much different materials and processes than the channels listed above.
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