I recently came across a post on some great tutorials by Aaron Blaise. For those of you who don′t know, he was an animation director at Disney and worked there for 21 years. He left to start up his own studio and offers training courses online in the hopes of making affordable art education and animation training accessible to everyone. You can browse through and purchase his training courses at creatureartteacher.com.
If a paid option isn′t for you, his YouTube channel is a great place to find a good mix of art tips and tricks. This playlist in particular www.youtube.com/watch?v=oUmV_gfAbxQ&list=PLnwHSDbcd45IC3aFVtfoqey5p1vhfoYSD is great. I′m slowly making my way through them in my spare time and I especially like that he has loose, organic, imperfect style that isn′t too technical or restricting. I can really relate as it shares some similarities with my own drawing style, like in this quick likeness study for example.
For more drawing exercises, you can take a look at Bobby Chiu′s YouTube channel https://www.youtube.com/channel/UCKfG25IfoxX8AT0JjmG2H0Q also. Bobby is one of those artists that I come across quite a bit, whether I′m looking for reference of just browsing through great art. He has some great drawing exercises like https://www.youtube.com/watch?v=qngGWhC-WUw, some of which go for over an hour! (Full playlist at https://www.youtube.com/playlist?list=PLeLw9TDyBUdU6sSCbqaSw7n5Jzjonj6nH).