Here's a pretty simple and interesting game I came across earlier today. The title is called January and the concept is just walking forward while catching snowflakes on your tongue. Each time you catch one, a single note is played. As you move forward, more and more snowflakes fall, causing faster and more complex music to play. At the same time, collecting a certain amount of snowflakes causes a poem to be read to you.
This is probably the most interesting, free, and simple game I've played since Digital Ai - A Love Story.