I've got rid of stuff through freecycle before, and I'm yet to be murdered. Perhaps have a friend / housemate there when they come to collect it if you don't feel safe?
Collection in person is generally fine.
I'd advise you to get the payment issues sorted before they turn up. Either pay through paypal (but as others have mentioned, it has it's downfalls) or explain you want the money up front.
If you are worried let friends/family know that you are selling something and they could keep an eye on you. If you feel really uncomfortable, keep a weapon nearby (but this is drastic and you'll likely never have to use it).
You'd probably do better advertising your things on Gumtree, rather than selling them on eBay and them taking a large cut.