Here is a great article that discusses business software as a tax write off.
"A dozen deductions for your small business"
"5. Software and subscriptions
The recently increased Section 179 provides another tax break in this area of business expenses. Previously, a company had to depreciate the cost of computer software over three years. Now, off-the-shelf software business buys can be fully expensed in the year purchased. As with the other expenses covered under this part of the tax code, the deductions are allowed for tax years 2003, 2004 and 2005.
The rules for deducting business and industry-related magazine subscriptions weren't changed. You can continue to take the total costs as a full deduction in the year spent. "