I don't know if I posted it here before, but this is my trick for starting my own garden plants. I make pots out of quart-sized yogurt or cottage cheese containers.
I have been thinking about doing something similar with plastic containers I get my powdered mix drinks in from WalMart. I would cut them in half, so one part would be the bottom section which I would drill in some drain holes, and the top part could use the lid with drain holes and just invert that portion.
One thing... these are big pots. It takes a lot of potting soil to fill them. That would be very expensive for the number of starts I do, 85 +/- this year.
Those plastic powdered mix containers are a lot smaller. Probably good for lots of plants but maybe too small for larger things and you would have to then up pot them later.
So I make my own potting soil. The compost I get out of my compost pile and chicken run is a BIG part of that.
I was going to use my chicken run compost for seed starting in the house, but then I watched/read that taking living soil and compost from outside is a terrible idea if you are starting your seeds inside the house. Lots of problems with gnats, aphids, etc... if you bring in living soil into the house.
My long-term goal is to build a greenhouse outside so I can use more of my own compost and save even more money. But this year I ended up purchasing sterile potting mix for my seed starting inside the house. It won't save as much money, but it will probably save the marriage because I don't think Dear Wife would be very happy if the house filled up with fungus gnats and the like.

Speaking of reusing those plastic powered mix containers, does anyone have some good suggestions for reusing them for different things? I have the type on the far left, the opaque light brown containers, which you really cannot see inside. I have saved maybe 30 of them and they are just looking for a second life. Any suggestions appreciated.