For home equipment, if all else fails, you can take it to the Household Waste Recyling Centre at Milton (Milton tip). This probably doesn't work for businesses.
This facility will reuse or properly dispose of it if they can't.
For computer equipment other than PCs, Jules Richardson suggests that the Computer Museum at Bletchley Park might be interested.
You may also be interested in IT-Green who can re-use or fully recycle your computers.