I've been resource gathering for YEARS so now I am going to share my dragons hoard
Floorplanner. Design and furnish a house for you to use for having a consistent background in your comic or anything! Free, you need an account, easy to use, and you can save multiple houses.
Comparing Heights. Input the heights of characters to see what the different is between them. Great for keeping consistency. Free.
Magma. Draw online with friends in real time. Great for practice or hanging out. Free, paid plan available, account preferred.
Smithsonian Open Access. Loads of free images. Free.
SketchDaily. Lots of pose references, massive library, is set on a timer so you can practice quick figure drawing. Free.
SculptGL. A sculpting tool which I am yet to master, but you should be able to make whatever 3d object you like with it. free.
Pexels. Free stock images. And the search engine is actually pretty good at pulling up what you want.
Figurosity. Great pose references, diverse body types, lots of "how to draw" videos directly on the site, the models are 3d and you can rotate the angle, but you can't make custom poses or edit body proportions. Free, account option, paid plans available.
Line of Action. More drawing references, this one also has a focus on expressions, hands/feet, animals, landscapes. Free.
Animal Photo. You pose a 3d skull model and select an animal species, and they give you a bunch of photo references for that animal at that angle. Super handy. Free.
Height Weight Chart. You ever see an OC listed as having a certain weight but then they look Wildly different than the number suggests? Well here's a site to avoid that! It shows real people at different weights and heights to give you a better idea of what these abstract numbers all look like. Free to use.
For anyone who hasn't seen them before, Hidden Search Operators are handy tricks you can use when you're either searching or filtering AO3.
summary: string is a generic way of explaining that you can search AO3 for a specific word that appears in a summary. You can do this from the search bar in the header, from the Any Field box at the top of the Advanced Search form, or from the Search Within Results box at the bottom of the filter menu.
Examples:
summary: Bruce
summary: "Bruce Banner"
summary: Bruce OR summary: Banner OR summary: Hulk
You need to put quotation marks around your search term if it is more than one word. The quotes make sure that the site searches for those two words together.
The other two operators listed work best in the Search Within Results box.
expected_number_of_chapters: 1 will return results where every fic has only 1 chapter currently posted.
You can use expected_number_of_chapters: -1 if you want results where every fic has more than 1 chapter currently posted.
otp:true will return results where there is only 1 relationship tag on the fic. If you want results where there are 2+ relationship tags (and no fics with only 1 relationship tag) then you can use otp:false