You can visit this map for the most accurate foliage report in Maine: http://www.maine.gov/doc/foliage/report/index.shtml

As for where to go, it depends on what you want to see. Kayaker has some good suggestions. One place that we visit every year (we live in Maine) is Gulf Hagas, it's essentially the Grand Canyon of Maine. It's 4 miles (8 round trip) of waterfalls and gorges.

Acadia National Park is great if you don't get stuck in the tourist traps. Go off the beaten path such as the Carriage trails. If you're looking for quiet places to kayak, Maine's a great place for that, just look at a map and have a vehicle that can traverse logging roads and get there. This is a good book for nice kayak locations: http://www.amazon.com/Quiet-Water-Ma.../dp/1929173652.