We are signed up at GreatNonProfits.org now.
If you have some time please write a review for us http://gr8np.org/go/sxV
Also we have some beta support for monthly bitcoin subscriptions. This is currently a manual process. I do have an IPN setup for this but it is not tied into the database system just yet. So if you choose to use this payment method let me know so I can ensure everything works smoothly.
We are using coinbase.com to provide subscriptions for bitcoin. Because bitcoin is a push technology (customer must initiate the exchange) subscriptions have to happen through an intermediary service, such as coinbase. Because of this you will need to setup a coinbase account if you want to use bitcoins instead of paypal. Bitcoin subscription buttons are now off the homepage (hive13.org) under the paypal buttons.
Craig