I thought this list of logos & analyses is pretty cool. They've got 25 clever logos with hidden tricky-bits, like the Fed-Ex logo below. Look at it for a few seconds...

Now look at the space between the "E" and the "X" and how it makes a forward pointing arrow, suggesting forward motion & speed.

This logo is for the Hartford Whalers hockey team. Check it out...

This has a triple whammy: the blue whale tail, a "H" in the negative space between the blue & green designs, and then a green "W". Smooth, right?