My wife will be receiving an inheritance from her Uncle's estate. What are the federal tax implications?
It depends on how big the inheritance was. According to the IRS you are in the clear unless the total assets she inherits exceed $1 Million.
Edit - In 2013, the amount one can leave and have no federal estate tax issue is $5.25M. It's the deceased's estate that pays the tax, not the beneficiary. So even if this were above the number, it's received post-tax. The article linked above is current.