The website for the interactive TBB has been moved to the following address:
http://www.ohaus.com/input/tutorials/tbb/tbbentry.swf
I have been using this interactive website prior to using a real TBB with my students, and it has made a huge difference in the ability of my 5th graders to read the balances accurately, esp with the 10ths place value.
The values are randomly generated and the students get instant feedback as to if they read the balance correctly or not. Sometimes, the answer is in the 100ths place, but I tell them that its impossible to really know what the hundredths place value is, and as long as their 10ths place value is correct, or close (0.78 = 0.8 g) their answer is ok. They have updated the activity, last year, almost every answer had a value in the 100ths place. So I was happy to see that change.
Here is the worksheet I use with the website:
http://www.middleschoolscience.com/tbbpractice.pdf