Your contribution limit is generally limited to your compensation. However, if you file jointly in 2008, your spouse can contribute the smaller of $5,000 ($6,000 if you are age 50 or older) OR the total compensation includible in the gross income of both you and your spouse for the year less your IRA contribution for the year to a traditional IRA (I'm assuming no Roth contributions).

This means that the total combined contributions that can be made for the year to your IRA and your spouse's IRA can be as much as $10,000.

Some exceptions may apply (esp depending on the type of income you both receive) so double check with your financial advisor before making the contribution.