If you do your laundry in an apartment laundry room or a public laundromat, check the discard bins for "empty" containers of soap, bleach, used Bounce sheets, etc. -- basically anything that can be reused or that is tossed out. 9 times out of 10 those "empty" laundry soap containers have at least one or two washes left in them.
Rinse the container thoroughly before discarding it. In fact, if you can fit it into your washer, go ahead -- it'll get out all the soap, it will clean the container, and you won't have missed a drop!
I'm working on figuring out how to take two tops from the same size and type of laundry detergent bottle, punch a hole through the top of each one, and fuse them together, so that I can turn one upside down on the other and strain out all the last bit of laundry soap.
Use a piece of aluminum foil in the dryer instead of a bounce sheet -- works just as well for removing static and is reusable.