When I repot all of my potted plants each year, I end up with a rather large amount of used potting soil. It seems like a waste of good organic material to take it to the landfill. Is there a way of saving and recycling it to make it usable in some way? Can it be composted?
Of course you can compost it! Clay soil improvement (@uncle brad) is another possibility.
I use it to fill small lawn gaps (I'm not into the bowling green quality lawns!) or to help top up raised beds (where the bulk goes).
The only thing to watch for would be possible disease. You may want to discard it if you had some serious disease (or nematode) problems in the plants which were in it. There the best thing would depend on the disease - a good hot compost heap may be sufficient to sterilise it.