I followed this excellent tutorial (at 0.5x speed) to create my own custom Solana token. I can send it to my wallet via command line. Now I want to do either free or low-cost airdrops. Is there a way to do this without having to spend a lot of my own SOL?
No matter what, in order to airdrop tokens, you'll need to pay for the rent-exempt reserve for the recipient's token account, which is 0.00203928 SOL for each person.
After that, you'll need to pay for the transactions to mint to all of these recipients. If your payer key is the same as the minting authority, that comes out to 0.000005 SOL per transaction, and you should be able to fit quite a few mintings in one transaction.
Take a look at https://github.com/solana-labs/solana/tree/master/tokens#distribute-spl-tokens for an easy tool to distribute tokens.