You can take them to the cargo tram in Zurich - it rotates around the city and takes goods that you can't fit into a Zuri-sack on a given date from 3-7pm. You have to walk, bike, or take public transit to use it though:
http://www.stadt-zuerich.ch/ted/de/i...nd_e_tram.html - it's free.
They've taken down the 2011 schedule, but, from my printed one, here are the remaining cargo dates for the year:
December 13: Hirzenbach
December 20: Letzigrund
December 15: Seebach
December 23: Strassenverkehrsamt
December 6: Tiefenbrunnen
December 22: Wartau
December 8: Wollishofen