This has been a good year for caterpillar spotting. There were two of these little fellas in my milkweed patch earlier this summer. They are most likely Unexpected Tiger Moth caterpillars. You can learn more than you would ever want to know about them here. As near as I can figure it, they are "Unexpected" because they are found in isolated populations only.
This handsome fellow was crawling on a blueberry plant in our Oak Openings Metro-park. I labelled him the "yellow shag carpet" caterpillar, until I was corrected on bugguide.net. He is a Spotted Apatelodes Moth caterpillar. It's a pretty cool name, although I like mine better.