... what do you do in terms of follow-up?
Four times I've either felt blessed by a pastor's sermons on the web, or their in-person sermons when they were supply pastor. And so I've sent their home church a small check. (By publicizing this, there goes my eternal reward!

) In all cases it would have been obvious from the letter that I'd never be able to attend worship, if only from the great distance. Anyway, I haven't ever received an acknowledgment. Sometimes I got to wondering if the check ever made it to them, etc., or frankly in cases where I knew the pastor personally, "Was it something I said?"
What say ye about the practice of sending of receipt letters? I guess I don't care so much about getting a hand-written letter of praise, or a tax-return receipt, but was left pondering about the process. If were in fact standard courtesy not to expect a busy financial secretary or senior pastor never to acknowledge random donations, that's okay too.
It's interesting there have also been cases where I visit a church once on vacation, making it clear I'm only on vacation. But they insist on my address and send me newsletters for a long time-- this seems to be the other side of the coin.