Well, let's see… I can't say as I have ever written to anyone JUST to thank them from the work they've done, but I've written for other reasons and managed to add some complimentary comments to my message.

It's easy now that most authors have web sites. (If they don't, I am told, you can always reach them through their publisher.)

I e-mailed James W. Loewen because I read on his web site that he was collecting information for a future book, so I sent him some information, and he thanked me, and we exchanged a few more e-mails.

Years ago, before e-mail, I sent a long letter to Jan Harold Brunvand, the collector of urban legends and maybe the guy who coined the term. I told him several of the stories I had heard, most of which were variants of stories he had already printed, but some were new, or so I suspected. He made one of them the subject of his newspaper column.

Also, I have e-mailed the owners of several web sites to point out errors. I always make a point of thanking them for creating the web site and posting useful information. (If it wasn't a web site that I liked and found useful, I probably wouldn't bother to e-mail them at all.) I have gotten gracious replies from most of them.