Paul Carter of Logikstate has just let me know that his iOS classic falling sand puzzler is now free on Android, both on amazon app store and google play.
I've had this game on my Nexus 7 for about a year and it's a great time waster with properly addictive game play. Now that it's free, of course, comes the inevitable ad support, but is now accessible to everyone with play store or amazon app store access.
'Slides is also available on iOS as a paid app
Sand Slides website
Sand Slides on Play store
Sand Slides on Amazon App store (UK link)