You'll find it difficult to get any charity to take 2nd hand furniture......apart from the logistics of transport and storage for bulky items, they are wary about possible legal implications......eg supplying a family with a sofa that turns out to be made with non-flame retardent material. I'd suggest using dublinwaste.ie - look or the "freetrade" link and advertise it there.
It could be worth putting an ad. in Buy & Sell. Even if you don't make money, someone might be interested enough to come and take it away. Its not charity but at least its recycling.