It's Deductible from Intuit

When you donate clothing, toys or other items to charity and want to get the biggest deduction possible, don't just guess what your donations are worth. Use ItsDeductible® to accurately value your donations in compliance with IRS guidelines and maximize your tax savings. It’s your own Blue Book for Donated Items.  FREE at http://www.itsdeductible.com/

Assign Accurate Values — Access thousands of values for the items you donate to charity, including consumer electronic items such as audio equipment, computers, cameras and more.

Instantly Transfer Into TurboTax — With a click of a button, you can instantly transfer your donation information into your 2004 TurboTax personal return*.

Prints Reports and Receipts — ItsDeductible puts everything you need on the right form and makes it easy to substantiate your deductions with donation receipts and reports.

ItsDeductible and "Preparing your Taxes"

While ItsDeductible does not directly "prepare your taxes" it provides valuable tax information you will need when preparing your taxes and several ways of delivering that information to your tax preparation software or tax professional. 

If you use TurboTax to prepare your taxes ItsDeductible exports data to a file that can be imported by most TurboTax products.  When importing the ItsDeductible data TurboTax will automatically populate the charitable donations section of TurboTax with the Non-Cash, Monetary and Mileage donations that you have entered into ItsDeductible.

Or if you do not wish to import directly into TurboTax; the ItsDeductible Donation and Expense Year-to-Date reports are available and provide all the information you or your tax preparer would need to enter your donation and expense information into a tax preparation software program manually.