Can a company who does not currently offer a qualified profit sharing plan, start one now and make a 2005 contribution if they have not yet filed their 2005 corporate taxes?

no because a qualified plan must be adopted before the end of the employer's 2005 tax yr, but the employer can adopt a SEP at any date up to the day the 2005 tax return is filed with extension which will provide the same tax deduction as a PS plan and the same max contribution.

Great...thanks for the help!