Boston Business Journal has a list of 2011 municipal tax rates that might be helpful. You can find it by searching 'Massachusetts real estate tax rates' on Google. I think in most cases rates have gone up slightly this year, but it'll give you a fair idea. The average rate is about $13-$15 per thousand of assessed value, but can go up to about $20 in towns like Wayland which have a very small commercial tax base. As mentioned before, some towns like Cambridge, Somerville and Boston have a residential exemption that is deducted from your tax bill if you live in the property- the full amount is paid only on rental properties.
Good luck with your move!
Assessed values and property values are not always the same.
Boston also allows a $1500.00 residential tax exemption, if you live in the property.