Depending on your income and age, a 401K may allow for greater deductions than a SEP. You can open a self employed 401K for you and your spouse (if your spouse is an employee of your business or has self employment income from a different business), through places like Fidelity or Charles Schwab. I'm not sure about Schwab but Fidelity does not have any fees to open or administer the account.
You get to deduct up to $14,000 each for the 401k ($18,000 if you are over 50), and another 25% of the your compensation (up to $42,000).
If your spouse has a 401k through a regular job, he or she can still have a self employment 401K at long as the total 401K deductions are not over $14,000 ($18,000 for 50+) limit, plus they can also do the 25% of compensation deduction.
You have until the day your taxes are due to make the contributions, but you have to open the account before the end of this calendar year to be able to use it for 2005.