The lowest value US stamp was the 1/2 cent. A couple different versions were issued.
$0.20
.75
Today (February 4, 2015) it is worth 80 cents US.
Worth 6 cents
A US first class stamp dated 2002 is worth face value only, and it's still valid now.
8 cents.
The US issued a Chester W Nimitz stamp.
39 cents
I have an old paper food stamp and i was wanting to know what it would be worth now. It's a 1999 $1.00 paper stamp. It's in great shape.
Air mail stamps are good for ordinary postage- your stamp is still worth 7 cents if unused.
50 cents if unused. Nothing if used.This must be the most common US airmail stamp.
That is Scott number US 2998 issued in 1995. A mint copy will cost you $2.60 and a used copy 30 cents.