As part of the tax law changes passed in December 2010, Congress set the amount of an estate's assets that can pass free of estate tax at $5 million for 2011, indexed for inflation. So, in 2012, the amount increases to $5.12 million.
Don't get too comfortable with this bounty, though. The current law is set to expire at the end of this year, with the applicable exclusion amount, as it's known, decreasing to $1 million. Congress will likely do something, at the last minute, again, to keep that from happening, but it is anyone's guess that that might be (perhaps an extension for another two years?).
I suppose that this is really only an issue for a fortunate, prosperous few.