If I make a significant donation to the Salvation Army, how many years can I carry the deduction forward?

[Critter]

You can carry over your contributions that you are not able to deduct in the current tax year because they exceed your adjusted-gross-income limits. You can deduct the excess in each of the next 5 years until it is all used, but not beyond that time.

[SweetieJean]

Be sure that you keep good records in case of an IRS query.
Any nonmonetary donation that is in excess of $5,000 requires a signed written appraisal by a qualified appraiser.