Should I pay off my mortgage early or invest the money?

imo, if your investment promises to yield more than the interest rate of your mortgage, then, it is wiser to invest.

Depends on who you want to give money to...the mortgage co or the US govt in the form of taxes.

You will rarely get as good a tax break as you do on the mortgage. Assuming you can afford the monthly payments, keep it. If you gave it up, you probably wouldn't invest that money each month; you'd end up spending it instead.

I'm assuming you've come into some money. Again, not knowing your age or circumstance, it's difficult to give good advice. Certainly invest it - and if you have a number of years before retirement, put it mostly into equities - I'd recommend an index fund from Fidelity or Vanguard - something like the Vanguard Total Stock Market Index.

If it is a large sum, consider dollar-cost-averaging it into the market, holding the balance in a high-interest saving account.

Why not both. Pay off your mortgage and buy a new house to rent out or flip. With your mortgage paid off you have an opportunity to invest in real estate. It's possible you'll still get the tax breaks form the new mortgage as well.

I would work on both. Be putting some money into investments, but also be putting some money toward paying off your mortgage early. Without payments, you will be able to invest even more and not have the risk of owing money to someone.

The tax break is not that big a deal. You're basically paying a mortgage company to avoid paying taxes on that money. You can accomplish the same thing by giving to a charity.