A simple tweet or item in a Facebook news feed will usually elicit a response from someone. It's easy to get rid of old computers and appliances this way, especially if you haven't been able to sell them on other sites. This should be your first step, as it lets your friends or people you know be aware of what you're selling. It's surprising how powerful and simple this is.
Then, if that doesn't work for you, you can either post an ad in the Facebook Marketplace or similar section in other social networking sites. Listing something in your local Craigslist is also a good idea. When we were moving and had too much stuff, we used Craigslist to sell off furniture and tech that we couldn't use.
A lot of people like getting second-hand tech because it's significantly cheaper than buying it new. If this doesn't work for you, then you can always try the Freecycle network.