mostly thingiverse. I'll look at others if i can't find it there but i rarely have to. it has the largest library ime. the search and discoverability ui takes some getting used to though

i mainly print functional things. ex. i just got a dewalt planer and looked for models associated with it and found a dust collection attachment that will work with my vacuum and parts that allow me to wrap the cable to the planer itself

some things i just design myself. i broke one of the arms on my sunglasses so i designed and printed a brace i could use with some super glue and heat shrink tubing to fix it.

all this was just yesterday