It's not recommended that fishing line be tossed in with other refuse as wildlife still encounters it in landfills.
However, if that's the only option, cut the line into short lengths (1-2 inches max) and make sure trash bags containing monofilament are secure.
Visit these sites to see monofilament recycling programs around the world...
Australia:
http://www.oceanwatch.org.au/out-work/tangler-bin/
http://www.ffc.org.au/Stainless%20Steel%20Hooks.html
http://www.qldlitter.com/pdfs/fishinglineguide.pdf
Bermuda:
http://www.bnt.bm/Environmental_and_Conservation/fishing_line_recycling.htm
California:
http://www.healthebay.org/news/2007/08_02_monofilament/default.asp
Florida:
http://www.fishinglinerecycling.org/
Kansas:
http://www.hwqp.org/
Louisiana:
http://www.houmatoday.com/article/20080706/ARTICLES/807060301?Title=Fishing-line-can-cause-problems-for-environment
New Hampshire:
http://earth911.com/blog/2008/08/07/fishing-line-recycling-bins-decorate-the-nh-coast/
New Jersey:
http://www.state.nj.us/dep/njcleanmarina/fishing_line_recycling.html
New York:
http://www.goingcoastal.org/fishingline.html
South Carolina:
http://saltwaterfishing.sc.gov/monofilament.html
http://deweesisland.wordpress.com/2008/10/30/monofilament-fishing-line-recycling-bins/
Texas:
http://mrrp.tamu.edu/
United Nations:
http://www.unep.org/regionalseas/marinelitter/
BoatU.S. Foundation:
http://www.boatus.com/foundation/Monofilament/
http://blogs.courierpostonline.com/fishhead/2009/08/24/sandy-hook-to-recycle-monofilament-fishing-line/
Federation of Fly Fishers:
http://www.fedflyfishers.org/Default.aspx?tabid=4401
Kayak Paddlers:
http://www.paddling.net/sameboat/archives/sameboat395.html
Marlin Magazine:
http://www.marlinmag.com/news/news/boatus-foundation-seeks-local-help-with-fishing-line-recycling-program-52746.html
Native American Kids:
http://www.nativevillage.org/Archives/2005/January%2012%202005%20News%20I%20144/Jan%2012,%202005%20%20Issue%20144%20%20V4.htm