Toby Padilla discusses on the TweetDeck blog the Android beta testers of TweetDeck. There are 36427 active beta testers. He list each of 246 phone models with its count and each of 111 software variants with its count.
http://blog.tweetdeck.com/android-ecosystem

36427 active beta testers
246 different phone models listed
111 software variants listed

He provides some pie charts of the variety.

"Android TweetDeck Beta Users by Phone"
http://posterous.com/getfile/files.posterous.com/temp-2010-10-12/JBccflqmrxyAyCsGxaimBBDcHlazGcftevgyqpDvGuvzHawkusqzrwkFwvfi/android_model_beta.gif.scaled1000.gif

"Android TweetDeck Users by OS Version"
http://posterous.com/getfile/files.posterous.com/temp-2010-10-12/JBccflqmrxyAyCsGxaimBBDcHlazGcftevgyqpDvGuvzHawkusqzrwkFwvfi/android_model_beta.gif.scaled1000.gif

One of the commenters provided an image of the first 100 Android devices.
"PercentMobile Android OS – The Firts 100 Devices"
http://analytics.percentmobile.com/images/first_100.png

other coverage:
pcpro: http://www.pcpro.co.uk/news/enterprise/361948/developers-battle-with-over-100-different-versions-of-android
slashdot: http://mobile.slashdot.org/story/10/10/14/1458200/Devs-Grapple-With-100-Versions-of-Android