The Bali Crisis Cente for Natural Disaster is collecting for Aceh relief. The site http://4aceh-sumut.kcbtours.com gives detailed accounts of what relief is being organised and transparent accounts of donations received. Rotary project.
Clear directions on how to transfer money.
I can personally vouch for the ethics of Al Purwa, his wife Marina and family. Rotary of course says enough.
If you are in Bali, drop around to KCB Tours, Jalan Raya Kuta No. 127, about 300 meters past Sanur turn out of Kuta and give what you can. Ask for Al, Marina, Barbara or Simon.
Otherwise, use the electronic means their website suggests.