The Stamp Act was one of the most important taxes in American history. Because American colonists were so angered by the Stamp Act, they increased their opposition to British rule in general. They protested very vigorously against the act, often with some degree of violence. This was one of the major factors in pushing the colonists towards rebelling against England.
If you look in the link below, you will see that a very great number of things were taxed under the Stamp Act. In general, we can say that many kinds of things that were printed on paper or on other materials were taxed under this act. For example, playing cards were taxed. So were legal documents like contracts, wills and diplomas. The paper on which newspapers were printed was taxed. Almanacs, calendars, and pamphlets were all taxed.
If you need a list that includes everything that was taxed under this act, read through the actual text of the act in the link below. However, it is generally adequate to say that the paper or other materials that most things were printed on were subject to being taxed.