I don't know about any organizations you can donate it to but if you don't find anyone and you gotta get rid of your machine, it looks like you can find someone to recycle it here:
> Apple Trade In lets you recycle any Apple device (including devices from Apple-owned brands) at any Apple Store and on apple.com for free. That includes your batteries and old electronic products as well as free, on-demand packaging recycling for our commercial, education, and institutional customers. When we receive your device it will be thoroughly inspected to determine if components can be recycled or reused. Whether recycled or reused all activities relating to the processing of your device will be managed in an environmentally responsible way.
Thanks for this!