|$1,173 of donations last winter (Cat not included)|
The deduction is generally limited to the fair market value of the item. There are many guides to determining the appropriate value (including IRS Publication 561) of your donations, but that value tends to be about 10 - 25% of the original cost - so we're talking about donations of items that originally cost somewhere between $40 - $100 billion! In just one year! That's a lot of stuff that is happily getting a new life, instead of wasting away in a landfill (figuratively speaking... landfills actually aren't very conducive to biodegration).
Any reuse is awesome, of course! But for a tax deduction, you need to be giving your items to a qualifying tax-exempt organization. Most such organizations will indicate on their website that they are a qualifying 501(c)(3) organization; they must also state this on the receipt they give you to document your donation. To confirm that a charity is in good standing with the IRS and qualifies for tax-deductible donations, you can check on the IRS's website.
Goodwill and the Salvation Army are common donation sites. There are also a myriad of other organizations, local and national, that often accept specialized items. Miss Minimalist has a list of 101 places to donate stuff.
See IRS Publication 526 or a professional tax preparer for additional details on the rules and documentation requirements.