I did search the forums for "Trash Bin" before i posted this, so i'm pretty sure no one has posted this yet. Also looked for "Trash Can". Both with quotes.
Trash Cans, could simply be bins that you place around your fort. I assume that there would be only a few select objects a Trash Bin would be used for however. The Trash Bin should be placed like a statue. It also should give some kind of boost to the value of the room its in, depending on the quality of the bin.
A few Trash Bins could be placed near a Dinning room, one could be just for seeds and the other could be for refuse. Once the seed bin gets filled, a hauler comes and takes the seed bin to the Seed stockpiles, and drops off the seeds where they are suppose to be. Then after which he returns with the trash bin. While the trash bin is gone dwarfs could still just drop there seeds off where the trash bin was, if at that time it is being emptied by a dwarf, then once the dwarf gets back and places the trash bin back, any seeds or refuse near it would then be automatically put into the bag.
If dwarfs cannot find a trash bin close enough to them, then they should do what they would normally do with refuse and such.
Trash Bins could also be useful for a few other things also.
Trash bins could become Clothing Hampers. If a dwarf has owned clothing, a Trash Bin can be set to a Clothing Hamper and could be a drop off point for dwarfs with dirty clothing that needs to be cleaned. Nobles or other more important people, or even all your dwarfs, could have a Clothing Hamper placed inside there room. They could then stick there dirty clothing in there which needs to be cleaned, depending on how many sets of clothing that particular dwarf has depends on when that dwarf or a servant would take it to a dirty clothing drop off point.
The whole bin itself could be taken directly to a dirty clothing stockpile, once someone cleans clothing they could clean a whole bin at a time, then the clothing are placed back into the bin, and then moved to a stockpile for clean clothing, which would then be transported back to its owner.
Once clothing becomes too raggy / damaged to be used anymore, it could also be tossed away into a trash bin.
Trash Bins for this, could be placed near a barracks, once people start loosing there clothing near the barracks, they could then just stick the dirty damaged clothing in a trash bin near them.
I assume a trash bin could be used for other things as well. Such as storing fish which you would have to take long distances. Make it so you could place a few trash bins near where your dwarfs are fishing. As they fish they fill up whatever empty bins are near them, once a fisher dwarf fills a bin up, he can then haul it to the nearest fish stockpile, then return with the bin.
Okay thats all i can think of for now.