Does anyone know how to sell used computer parts?

Id personally go with craigslist or ebay.

In London there are shops that specialise in trading in second hand computer parts. Maybe there is something similar in NY.

I can’t think of any place that will give you cash for them, except maybe as recyclables. eBay or some of the geek websites that allow members to sell stuff.

I’ve sold parts on ebay and craigslist

There are such shops out there (I remember one near St. Paul, MN), but I don’t think there are very many. Depending on what it is you’re trying to sell, eBay is a great bet. If it’s a recognizable product (graphics card, for example), you might try selling on Amazon, as well. I sold a used Canon camera charger and battery there, it was easy peasy, I got a good price for it, and I feel a bit more confident about the transaction there than on eBay.