I believe that each can contribute up to $5k (total $10k) if married filling
jointly.
See IRS Publication 590:
Spousal IRA Limit
For 2010, if you file a joint return and your taxable compensation is less
than that of your spouse, the most that can be contributed for the year to
your IRA is the smaller of the following two amounts:
$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, reduced by the following two amounts.
Your spouse's IRA contribution for the year to a traditional IRA.
Any contributions for the year to a Roth IRA on behalf of your spouse.
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 ($11,000 if
only one of you is age 50 or older or $12,000 if both of you are age 50 or
older).
Note.
This traditional IRA limit is reduced by any contributions to a section 501(
c)(18) plan (generally, a pension plan created before June 25, 1959, that is
funded entirely by employee contributions).
Example.
Kristin, a full-time student with no taxable compensation, marries Carl
during the year. Neither was age 50 by the end of 2010. For the year, Carl
has taxable compensation of $30,000. He plans to contribute (and deduct) $5,
000 to a traditional IRA. If he and Kristin file a joint return, each can
contribute $5,000 to a traditional IRA. This is because Kristin, who has no
compensation, can add Carl's compensation, reduced by the amount of his IRA
contribution, ($30,000 – $5,000 = $25,000) to her own compensation (-0-) to
figure her maximum contribution to a traditional IRA. In her case, $5,000
is her contribution limit, because $5,000 is less than $25,000 (her
compensation for purposes of figuring her contribution limit).
