If you bought a home in 2007 and are paying PMI, or private mortgage insurance, those payments are tax-deductible. Recently, this tax deduction rule has been extended to apply to loans closed in 2008.
Check with your tax professional, because I don't even pretend to know the in's and out's of the IRS tax code. But I heard it from my tax guy, while he was giving a short presentation to a group of Realtors. I trust he knows what he's talking about, but just don't have the details you might need to claim the deduction on your taxes.