Does your wife have any income herself? This may be a bigger determinant than her short history.

If she does not have any income herself, a card from your bank would be a good place to start. Banks often issue cards to people in her situation. There was also a recent announcement that dealt with reporting income for "stay at home moms" that might be indirectly applicable in this situation. I believe it would allow your wife to list your income as assisting with repayment. Check on this before doing that, however.

If your wife does have income herself, this becomes a much broader question as to spend habits, what rewards to you want back, what banks weigh income more than credit history, etc.

I would stay away from store & gas cards unless you are really a hardcore shopper at one of these. These cards are a PITA, and not all of them report regularly on your credit history.