Items that you (us in general) don't know how to reuse; like office chairs for instance,
can be donated and reused by someone else. (I recently picked up a better office chair at Goodwill
and it set me back a whooping $3.00)

So I just donated the one I had back to the same store.
Filing cabinets could be used in a variety of ways (besides storing paperwork)- in a garage or shed for gardening
supplies: pots, bags of soil, small hand tools, gloves-etc. Or as storage for pet supplies; what we put in
those drawers is only limited by our imagination (and needs)
They could house boxes too to hold stuff we want to recycle.
Shelving units can be used for a variety of things and in other parts of the house like the kitchen, for instance,
if someone lacked cabinet space.
I like to watch "Find and Design" It's a flea market, garage sale decorating show (here locally
on the Biography channel-check your listings). It's amazing how the decorators find old
items and re-purpose them and it gives me tons of ideas; either by recovering items
with tiles, paint, new stain, new handles or even cutting items into pieces to reuse parts
of them.
This site also has many idea's on reusing items.
http://www.bobvila.com/
Hope that helps.