Stigma2 is that old favourite,
Stigma, with the added feature of external level support.
If you aren't familiar with the original, here is a quick rundown of the game:
You are a ball bearing on a super-smooth surface. You have to collect a series of 'orbs' from this surface, and then return to the starting point. It is based on a Psion3 game of the same name.
New (and improved features):