I am looking for a large list of ordinary differential equations, as a practice resource.
Preferably the list should be in order of "difficulty" and allow me to practice the different techniques (change of variables, etc).
Do you have a suggestion for a good list like this?
Here are some sources you might want to check out
I suppose it is worth mentioning The Differential Equations Problem Solver by D. R. Arterburn, Staff of Research & Education Association. I have never cared for these and although I own it, I hate the typesetting and also hate trying to locate things in it - so hardly use it, but it has a lot of worked examples.
Lastly, in India, various authors have written many problem books (teach by massive problem solving - an interesting approach that we have abandoned) and you can search those out.