Yes. As long as the stamp was issued after 1867 and is still unused, it doesn't matter the denomination. It is still postage.
49 cents today.
98 cents
44 cents today (May 2009) for a standard 1st-class stamp.
The cost of a First Class US postage stamp in 1968 was 5 cents. It was raised to 6 cents on January 8th. It stayed at 6 cents until 1971 when it went to 8 cents.
44 cents (as of June 27th, 2009)
35 cents
Yes and no. You can apply the Lady Liberty stamp from 2006 toward postage. But you will have to add 3 cents worth of stamps in addition. The Lady Liberty stamp is worth 39 cents. Today 1st Class postage is 42 cents. As of this writing (June 2009) first class postage is 44 cents, so you need to add 5 cents.
Today (February 4, 2015) it is worth 80 cents US.
No, it is not. It was a non-denominated postage stamp issued for the rate change in 1985 to 22 cents. It can be used for 22 cents of postage within the US, so two of these will mail a First Class letter today.
As of August 2021, the cost of a first-class stamp is 58 cents in the United States.
As of today 45/100 of a dollar or 45 cents
If you are talking about the Canadian stamp it is worth: Mint in Very Fine Condition around .30 cents Used in Very Fine Condition around .25 cents