An online platform where you can give away, buy, and sell new and used items. 

Some karung guni and scrap dealers also operate on Carousell and offer to buy recyclables.

Carousell even has a free section 

Warning:  many users in our community report that “no shows” and unreliable “buyers” are more common when there is no price.

Pro tip: want to give your item away but don't want to be bombarded by people who just anyhow chope for free stuff? Listed it at a very low price (eg $0.50) and then only people who find your listing on search will contact you. You can always refuse payment later.