Need dungeons to explore and demons to fight before the release of Diablo III? Side-scrolling exploration platformer Momodora III won't be ready until later this year, but this free demo includes three of the seven intended areas, with plenty of adorable boss battles and tricky jumps. The game follows Momodora II fairly directly, as protagonist Momo journeys to Hell to save her sister with a weaponized maple leaf. Of course, plot isn't all that vital, and the demo stands alone as a fun way to spend a few hours. The developer is also still taking feedback, so you've got a chance to suggest improvements to the art or gameplay.
The first Momodora platformer was released a couple of years ago, and both it and its sequel are free online here, although all the games sadly appear to be Windows-only. The developer suggests you play the second, which improved on the original in a number of ways. You can also follow the game's current progress on the dev blog.