Cuneiform is a script used to write a number of languages of the ancient Middle East, such as Sumerian, Akkadian, and Hittite. Since version 5.0 Sumero-Akkadian Cuneiform is part of Unicode, but until recently there have not been any fonts publically available. Now you can download one for the Hittite version of the script here.
Cuneiform was used for such a variety of languages over such a long period that the form of its glyphs showed considerable evolution over time and place. Thus different fonts are required to correctly display the forms used in Neo Sumerian (which appear in the Unicode charts), and those used in Old, Middle, and New Babylonian and Assyrian, Hittite or Elamite.
The only way to input Cuneiform at present is via the Character Palette or copy/paste.
Here are some test pages for Hittite, Akkadian, and Sumerian.
Different, alphabetic cuneiform scripts are also used for Old Persian and Ugaritic. For info on fonts and keyboards for these, see the blog entries for Unicode 4.1 and Unicode 4.0.