The maximum contribution is $5,000 a year ($6,000 if you are 50 or older). Same for your spouse. However, you cannot contribute more than your taxable compensation for the year. If you were part of a 401k retirement plan that went bankrupt, you may qualify to contribute more if you meet all the requirements. You may not be able to deduct the full amount if you or your spouse is covered by a retirement plan at work.
More details can be found at http://www.irs.gov/pub/irs-pdf/p590.pdf