They come from various artists of different skill levels. Source Film Maker or SFM is the name of the program that created those animations and they have a bit of a community. I have a lot of the good artists saved on my bookmarks and i follow them on tumblr too so it updates my dashboard. Since its a community and they use the same program and mostly use the same website to update each other its easy to start following people. I started following this person named blackjrxii on tumblr but he did mostly my little pony futa gangbangs which wasnt really my thing. But i could see who he followed so i would go to those peoples tumblr sites and then look at their followed list etc etc. Thats how i built up my bookmark list and why i have mostly good animators on that list.
Ohh and most of the ones from my previous link put watermarks on their animation. If it doesnt have a full link you can just google their name and then tumblr or deviantart. Usually when i see a animation with a watermark thats what i do to track them down. I saw an animation and the watermark simply said "Nyl" so i did a google search for Nyl Tumblr and Nyl Tumblr SFM and i found their tumblr site.