Below, you can see where the oil drain plug is located on my wood chipper. If I unscrewed it, it would send a cascade of oil down into the chipping drum, coating the blades.

Obviously that's no good. I solved the problem using the lid of a plastic spinach container from the supermarket. (Apologies for the poor photo quality.)

I cut the lip off all around, yielding a flat sheet; cut two notches near the corners of one end; and put a rubber band in the notches to squeeze that end into a funnel shape, while the other end remained flat, so I could tuck it under the drain plug. (As a bonus, the spinach container became the drain pan.)

It only cost me $4.99, and I got a few days' worth of iron, fiber and vitamin A out of it. I'm able to re-use the makeshift funnel for my lawn mower as well. However, it has its limitations; because the plastic won't hold its shape naturally I can't get it around an oil filter, for instance. This Flexible Draining Tool might be a better solution:

It's a sheet of aluminum alloy coated in nitrile rubber. The manufacturer says it will work in temperatures from -30 degrees Fahrenheit up to temperatures that none of us could survive in. It runs $12, which isn't bad, but you won't get any spinach out of it.