If you itemize deductions on your tax return, tax deductible charitable donations can be another way to reduce your total taxes.
There are at least a couple of valuation tools on the internet that make calculating your donation so much easier. I remember trying to value donations in the mid '90s and it was always a guessing game.
First of all, if you use TurboTax (and even if you don't), there is ItsDeductible. You can put in the value of non-cash and cash donations, and then when you are preparing your taxes you can import the total straight into TurboTax.
Even if you don't use TurboTax, you can still use ItsDeductible, keep a printout for your tax records or tax preparer, and just put the total of your contributions in your tax return (or give it to your tax preparer).
The Salvation Army also has a valuation tool for charitable donations. It's not interactive but still useful.
One tip for using ItsDeductible, as you finish a page, click to add your items from that page even if you have more to add later. It will not remember them once you leave that page if you don't add them. I entered an entire contribution once and then thought I could just hit "add" and it would take everything I'd entered. I figured it out the hard way.