According to the Sims Wiki, "Sims skilling up in the Inventing skill can collect scrap for their inventions, either by digging through junk piles or by detonating objects. Sims can also salvage regularly spawning burnt and broken objects. SimBots can also eat scrap at the junkyard."
World: Appaloosa Plains
Name: Pick 'n Pull Junkyard
Size: 20 x 30
Cost: N/A
World: Aurora Skies, Isla Paradiso, Lucky Palms, Lunar Lakes, Monte Vista, Starlight Shores
Name: Grady’s Junkstop
Size: 20 x 30, 30 x 20, 20 x 30, 40 x 20, 20 x 30, 30 x 35
Cost: N/A
Note: Automatically placed when Ambitions is installed.
World: Twinbrook
Name: Juan's Pick 'n Pull
Size: 30 x 20
Cost: N/A
Note: Actually classified as a "junkyard with no visitors".
World: Twinbrook
Name: Bayless Memorial Junkyard
Size: 60 x 60
Cost: N/A
Which is your favorite Junkyard?