Depends on a lot of factors, like the model, the specs, the shape it's in, etc. I'd say it's probably worth $50 or less. You can sell on a website called Low End Mac Swap, eBay (not recommended because of fees), or Craigslist. If you post a lot on here, or you can try and reach the rank that lets you into the Marketplace. Lastly, someone may PM you if they want to buy it.