For 2006 and 2007, you can contribute up to $4,000 or 100% of your earned income, whichever is less, each year to a Roth IRA. If you are 50 are older, you can contribute an additional $1,000 per year.

To contribute, you must have earned income - meaning a salary or self-employment income. Also, if your income falls within a certain range for your tax-filing status, your contribution will be limited. If it exceeds the top end of that range, you cannot contribute at all. These limits depend on your filing status and change each year.

If you are married, you and your spouse can each open a Roth IRA. You can each contribute up to $4,000 a year ($5,000 if older than 50) into your accounts, even if your spouse does not work, as long as you and/or your spouse earns at least as much as your combined contribution.

You can contribute to a Roth IRA at any age, even if you are covered by a pension plan at work, as long as you meet the other requirements. You can also contribute to a Roth IRA for your spouse if you don't exceed the income limits.

Note: These contribution limits apply to all traditional and Roth IRAs combined.

To see income and contribution limits for 2006 through 2009, see http://www.finance.cch.com/sohoApplets/RothvsRegular.asp. This site also has a calculator that lets you compare traditional and Roth IRAs.