This is somewhat involved. You can always contribute your $1000 of earned income into an IRA. However if you want to do more than that there are lots of issues.
Above the $1000, If you want to have an IRA (or extra IRA contributions) under your name your IRA deduction is then ruled by the spousal IRA rules. In this case you use the earned income of the spouse to qwualify for IRA deductions.
Is your wife covered by a qualified retirement/401k plan ? that may make a difference. I assume that you were not based on the checked box comment.
If your wife is an active participant in an employer pension/401k account then you can make deductable contibutions up to the $6k limit provided that your AGI income is less than $159k in 2008. The deduction then phases out up to $169k AGI income. However for the (active participant) spouse their deductable IRA contribution starts to phase out at $85k and is totally phased out at $105k AGI.
Here is a website that lists the rules:
The IRS also has a publication that describes the rules.