Try facebook, for a sell it page near you, I have a local one with over 3000 members, as fast as I was listing which is free, it was selling, made around £200 in one evening and then spent a day letting people turn up and take it. No fees for buying or selling anything, kids stuff flew from it.
Have you thought about NCT nearly new sales? The way the one near us works is that you label items with price etc., drop them off in the morning and go back at the end of the sale to collect any unsold items. The NCT take a % and the advantage is that you don't have to faff about with posting stuff like you do on eBay and you don't have to give up a whole day like you do with a car boot sale.
If its worth more than a couple of pounds Ebay, the rest we go to the car boot once a year last year did £300 on stuff we would have thrown out. We wait till at least Easter / early summer and pick a dry day, take a barbeque and cook breakfast whilst we tout our wears, its afun morning out but an early start. Clothes that dont sell we weigh in for 50p a KG locally. Ebay is expensive and some times its better to use the small ads on a forum like this one etc EG we are selling our camping trailer, Ebay would charge about £20 comission fees etc, so I have advertised it on some free ad sites, Preloved etc