I love this thread - this is fun!
The very cheapest things I have done include picking up stuff left out on garbage day from people who were moving. I found great stuff including food, toiletries, cleaning products, clothes. I also have furniture, lamps and two beautiful, large rugs from the side of the road.
I reuse tea bags (I like three used bags for a new cup to get the right strength.) I reuse all kinds of bags for lunches or storing veggies - anything I used to do with a ziplock. I use cloth bags for shopping and get plastic shopping bags from my family to use to line the garbage cans. Newspaper plastic bags are used to clean up after the dog.
When going out to dinner with friends, when I see that they aren't going to take home their leftovers, I ask if I can box them up and take them home. It is surprising, but I've never had any negative looks or comments from this - usually people are happy that the food isn't going to waste (begs the question why they don't take it home themselves.)
I have a reputation among friends and family that I will take any and all clothing. I take what I want for myself first, then give stuff to other friends and family, then give the rest to Goodwill and get a tax write-off.
I have repaired holes in socks and underwear to make them last longer. The majority of my socks are second-hand (but not the underwear.)
I also scrounge around in the recycle bins at school for the Coke points and get free Cokes that way (totally free since I never bought the product in the first place.)
Keep the posts coming so we can all get some new ideas!
Alison in Pittsburgh