see displaytag/dependencies.html for the list of dependencies needed by displaytag.
If you use maven 2 in your project all you need to do is adding the following to the dependencies section in your POM. Maven will take care of including all the needed libraries for you.
<dependency>
<groupId>displaytag</groupId>
<artifactId>displaytag</artifactId>
<version>1.2</version>
</dependency>
Starting from the 1.1 release optional modules are distributed as additional jars. Any module could require additional dependencies: