Some companies are now packaging tomato paste in tubes. This is a good idea, but:
a) many stores don't carry them
b) tubes are usually not recyclable, containing a mix of polyethylene and aluminum.
So, instead of wasting paste from a can or buying a tube, I just freeze any unused paste in an ice cube tray, and bust out a cube or two when I need some.
If you try this yourself: be forewarned that the paste doesn't get the consistency of ice -- it will remain sort of soft even when frozen.
When you want the paste, just microwave it or put it in a glass and put the glass in some warm water to soften the paste.
Do you have any great household tips to reduce waste?