<servlet>
   <servlet-name>jsp</servlet-name>
   <servlet-class>org.apache.jasper.servlet.JspServlet</servlet-class>
   ...
   <load-on-startup>3</load-on-startup>
</servlet>

<servlet-mapping>
   <servlet-name>jsp</servlet-name>
   <url-pattern>*.jsp</url-pattern>
</servlet>

Extension-List: extension1 extension2 extension3

extension1-Extension-Name: uk.co.datadisk.extension1
extension1-Specification-Version: 1.0
extension1-Implementation-Version: 0.8
extension1-Implementation-Vendor: Datadisk
extension1-Implementation-Vendor-ID: uk.co.datadisk
extension1-Implementation-URL: http://www.datadisk.co.uk/extensions/extension1

<context-param>
   <param-name>title</param-name>
   <param-value>Datadisk Web Application Example</param-name>
</context-param>

Note: you can have many of these context-params, they are just key-value pairs that can be used by the Web application

<filter>
  <icon>/images/icons/filter.gif</icon>
  <filter-name>Compressor</filter>
  <display-name>Compression Filter</display-name>
  <description>This filter applies compression</description>
  <filter-class>uk.co.datadisk.utils.CompressionFilter</filter-class>
  <init-param>
    <param-name>compression_type</param-name>
    <param-value>gzip</param-value>
  </init-param>
</filter>

Note: as you can see the <filter> element has many subelements that can be used, see the <filter-mapping> to how you map your filter

<listener>
   <listener-class>uk.co.datadisk.listeners.ExampleListener</listener-class>
</listener>

Note: see Tomcat advanced features for more information on listeners

<servlet>
  <icon>/images/icons/downloadServlet.gif</icon>
  <servlet-name>downloadServlet</servlet-name>
  <display-name>File Download Servlet</display-name>
  <description>This is a servlet for downloading files</description>

  <!-- you can use a JSP file instead of a servlet
     <jsp-file>/admin/users/ListAllUsers.jsp</jsp-file>
  -->

  <servlet-class>uk.co.datadisk.utils.downloadServlet</servlet-class>
  <init-param>
    <param-name>require_tc</param-name>
    <param-value>true</param-value>
  </init-param>
  <!-- make sure that the servlet has been loaded into memory
  -->
  <load-on-startup>3</load-on-startup>
  <!-- uncomment if Servlet must be run in user role
  <run-as>
    <description> This server does not require authorization to resources</description>
    <role-name>admin</role-name>
  </run-as>
  -->
</servlet>

<session-config>
  <session-timeout>40</session-timeout>
</session-config>

Note: there are a number of other subelements you can use i.e <timer-keep-alive>

<mime-mapping>
   <extensions>cvs</extensions>
   <mime-type>application/x-msexcel</mime-type>
</mime-mapping>

Note: there will be lots of different mime-type settings

<welcome-file-list>
  <welcome-file>default.jsp</welcome-file>
  <welcome-file>index.html</welcome-file>
  <welcome-file>index.htm</welcome-file>
</welcome-file-list>

Note: the above is the default anyway, but you can configure whatever you want

<security-role>
  <description> some description</description>
  <role-name>administrator</role-name>
</security-role>

Note: security is discussed here

<env-entry>
  <description>some description</description>
  <env-entry-name>MinimumValue</env-entry-name>
  <env-entry-value>5</env-entry-value>
  <env-entry-type>java.lang.Integer</env-entry-value>
</env-entry>

Note: in the java code you would use something like below to obtain the value

/* Obtain the initial context */
Context initCtx = new InitialContext();
Context envCtx = (Context) initCtx.lookup("java:comp/env");
/* Lookup environment entry */
Integer minValue = (Integer) envCtx.lookup("MinimumValue");

<ejb-ref>
  <description>some description</description>
  <ejb-ref-name>Employee Bean</ejb-ref-name>
  <ejb-ref-type>EmployeeBean</ejb-ref-type>
  <home>com.foobar.employee.EmployeeHome</home>
  <remote>com.foobar.employee.Employee</remote>
</ejb-ref>

Note: I discuss MBeans here