Electronic waste includes anything that has a plug or uses batteries (computers, printers, keyboards, monitors, televisions, stereos, microwaves, faxes, VCRs, cell phones, etc.). These items can contain large amounts of lead and other heavy metals, and should not be put in the landfill where they will leak and possibly contaminate the watershed.
The law in Colorado prohibits anyone from disposing of electronic waste into a Colorado landfill, as of July 2013.
Electronics should be recycled at the Pitkin County Solid Waste Center (landfill) for a small fee. Or, if you don't mind holding on to your items, the Environmental Health Department hosts an electronic recycling event in Aspen every year right around spring clean up time.
Visit EPA's site for a map of all Certified Electronics Refurbishing and Recycling facilities in the US.