The Washington Post had a good list of places you can donate to in order to help https://www.washingtonpost.com/world/2021/04/28/heres-how-help-india-covid/

Interestingly (to me at least) American Association of Physicians of Indian Origin is sending oxygen concentrators to India. That had been my original thought, but they cost about $500, and I have no idea where to send it - this lets me chip in towards one https://events.aapiusa.org/medical-oxygen-iama/. Given the conditions there, each concentrator represents one or more lives saved (many survive with just supplemental O2).