Google's own developer figures suggest that the vast majority of active Android devices are on two of five different Android releases. Also, Donut and Eclair are officially dead.
That last bit shouldn't be too much of a surprise, as the current version of Google Play only supports Android 2.2 ("Froyo") devices and above. The data, which Google tabulates to allow developers to target applications based on real world user interaction with the Google Play store over a 7 day period ending on the 4th of September US time shows that the most common version is the Jelly Bean 4.1.x variant with 36 per cent of all users, while all iterations of Gingerbread account for 30.7 per cent.
Honeycomb has the lowest penetration at 0.1 per cent of all devices, and as noted, Donut and Eclair are off the charts due to incompatibility, but then Google's own figures suggest that they accounted for less than 1 per cent of the total when previously tallied. The figures would also suggest that smartphones still far outrank tablets when it comes to Android users, with smaller screen sizes far more common than larger ones.