Is there anything else that either of us can do? Could she open a SEP, or something else? Or, are we together limited to nothing but my 401k?
DJ
As other people have suggested, non-deductible contributions should be considered. I opened a traditional IRA last year with non-deductible funds and plan to convert to a Roth IRA in 2010 when the income exclusion limit on conversions is eliminated (or when I ER). Since I've already paid taxes on these contributions, I will pay taxes only on the gains. Of course, this assumes no significant changes to the tax law.
In addition, you might consider non-deductible contributions to your 401k if they are allowed by your employer. I believe the current IRS 415c limit is 46K for 2008, meaning that you can make considerable after-tax contributions in addition to your deductible 15.5K and employer match.
Also, you may be able to roll after-tax 401k contributions (and corresponding gains) into a traditional IRA after you leave your employer, and then convert to a Roth IRA in the future. Before and after-tax contributions to a 401k are tracked differently as independent sources. I am told by Fidelity and others that you can roll over either or both as separate entities into a traditional IRA. In this way, you can generate a traditional IRA funded with after-tax contributions (and their taxable gains while in the 401k). If the funds were not in the 401k for a long period of time, the gains will be small, and your tax liability when you convert to a Roth will be small.
Even without the Roth conversion, the advantage of after-tax contributions is that distributions will compound tax free. Of course, you will need to pay taxes on the gains when you withdraw the funds. These taxes may or may not be greater than the taxable gains you will pay if you instead had the money in a taxable index fund (for example). It is a function of expected income and capital gains tax rates now and in the future. For most people, I think there is a financial advantage to non-deductible contributions. A disadvantage is that the money will not be available for use without penalty until you are old enough to receive distributions.
Personally, I basically do all of the above. I max out my deferred contributions to my retirement plan (currently a 401k, previously a 403, 457, and 401a). I max out my after-tax contributions to my retirement plan and to my non-deductible IRA. Then, I contribute to low cost index funds in taxable accounts.