I do this often and it is something that everyone not only appreciates but sometimes their favorite email of that day.

Even a simple email like "I really like the design of your website/blog" will make their day.

I once complimented a blogger for composing a particularly eloquent sentence. My compliment was concise and sincere.

All I received in reply was “Thanks!”.

I was thrilled. I earned an exclamation point from an academic who would never deign to use such punctuation lightly.