It's the most significant new tax law in a decade, but what does it mean for you? Big savings for millions of taxpayers, more if you have young children or attend college, a lot more if you're wealthy.

The package, being signed Friday by President Barack Obama, will save taxpayers, on average, nearly $3,000 next year.

But many families will be able to save much more by taking advantage of tax breaks for being married, having children, paying for child care, going to college or investing in securities. There are even tax breaks for paying local sales taxes and using mass transit, and a new Social Security tax cut for nearly every worker who earns a wage.

Most of the tax cuts have been around since early in the decade. The new law will prevent them from expiring Jan. 1. Others are new, such as the decrease in the Social Security payroll tax. Altogether, they provide a thick menu of opportunities for families at every income level.

"The tax code wants to encourage people to invest in their homes, invest in their education, invest in their retirement, and you have to know about all of these in order to take advantage of it," said Kathy Pickering, executive director of The Tax Institute at H&R Block.