Be careful about donating clothes
One of the main reasons these clothes go waste is that their intended recepients are not beggars, but proud people hit by circumstances who don't necessarily want old, faded hand-me-downs, which are also sometimes inappropriate given the kind of lives they lead. However, if the NGO concerned is making an effort to make those clothes presentable and acceptable to those they are intended for, as the Rotary Club of Chennai did after the tsunami, then it might be worth it. Otherwise they will just end up piled up on the streetside.
Gaurav brought this subject to my attention now, and has posted about it here.