Well, doing research is just doing research. Nothing creepy or stalkerish about that

But, actually sending someone something to their home address may be a bit invasive IMHO. I guess it would depend if the address was a matter of public knowledge.

I'm thinking proper protocol might dictate that it's ok to send someone correspondence at their place of business though.

Hmmm... I think the best bet might be just to contact them via their email and just tell 'em, "Hey! I'd like to mail you something as a token of my appreciation. Where can I send it?" No harm in asking.