Winter Fundraiser 2020

Walmart Gift Cards: These are great and simple and safe. Just pay cash and mail it to us. Maximum value: $1000.

Money Orders: If you live in the US, this is a safe and anonymous way to send money. Money orders are sold at major grocery chains like Walmart, local banks, and the US Post Office. Here is an article describing how they work.
And here is a list of stores that sell them: 

Money orders have a ‚from‘ and ‚to‘ field, which need to be filled out for us to cash them. Buy the money order with the fields empty, and in the ‚to‘ field, fill in by hand our corporate info: Insider Media LLC, PO Box 22, Greenwich, CT 06836. Send us the money order with the ‚From‘ field left blank.

To ensure anonymity, pay for the money order with cash. It is often not possible to use credit cards to buy them, and it isn’t advisable, because you get hit with a cash advance fee, although debit cards can be used. The maximum amount for money orders varies between $500 and $1000, depending on the vendor.

Cash: People send us cash all the time, and we have never had it go missing. You can include an email or street address where we can write you back and confirm receipt. (And say thanks!)

A common misconception is that this is illegal in the US, or somehow unsafe. It is not illegal, and it is very safe, as millions of grandmothers who have slipped a $20 bill in a birthday card can attest.

Another misconception is that the USPS scans mail and can detect cash in an envelope - they don’t. Just make sure the envelope is reasonably thick, and fold the cash in a piece of paper, so that someone can’t see the bills through the envelope.

For added peace of mind, from the US, you can send it using priority mail with delivery confirmation or signature confirmation. That way you know your letter arrived.

Here is a discussion in Quora about how reliable it is.