They're not a tax write-off but like someone already said, that money is taken out of your paycheck before taxes, so it's not really that big of a hit you're taking.

Find out if your company matches you, and if so, up to what percent. 6% is pretty common and what I'm in for. You can't beat a 100% return on your investment. That's free money.

If you still have money you'd like to sock away for old age look into IRA's. If you're young, the Roth IRA is the way to go because when you take that money back out when your a geezer, you won't have to claim it as income because you already paid taxes on that money.