As of maven-assembly-plugin-2.2-beta-2, there are 4 pre-defined descriptor files:

bin.xml

<assembly>
  <id>bin</id>
  <formats>
    <format>tar.gz</format>
    <format>tar.bz2</format>
    <format>zip</format>
  </formats>
  <fileSets>
    <fileSet>
      <includes>
        <include>README*</include>
        <include>LICENSE*</include>
        <include>NOTICE*</include>
      </includes>
    </fileSet>
    <!-- TODO: docs? -->
    <fileSet>
      <!-- TODO: use expresssions instead: ${project.build.directory}, ${project.build.finalName} -->
      <directory>target</directory>
      <outputDirectory></outputDirectory>
      <includes>
        <include>*.jar</include>
      </includes>
    </fileSet>
  </fileSets>
</assembly>

jar-with-dependencies

<assembly>
  <!-- TODO: a jarjar format would be better -->
  <id>jar-with-dependencies</id>
  <formats>
    <format>jar</format>
  </formats>
  <includeBaseDirectory>false</includeBaseDirectory>
  <dependencySets>
    <dependencySet>
      <outputDirectory></outputDirectory>
      <outputFileNameMapping></outputFileNameMapping>
      <unpack>true</unpack>
      <scope>runtime</scope>
    </dependencySet>
  </dependencySets>
  <fileSets>
    <fileSet>
      <directory>target/classes</directory>
      <outputDirectory></outputDirectory>
    </fileSet>
  </fileSets>
</assembly>

project

<assembly>
  <id>project</id>
  <formats>
    <format>tar.gz</format>
    <format>tar.bz2</format>
    <format>zip</format>
  </formats>
  <fileSets>
    <fileSet>
      <!-- TODO: use expresssions instead: ${project.build.sourceDirectory}, etc -->
      <directory>.</directory>
      <outputDirectory></outputDirectory>
      <useDefaultExcludes>true</useDefaultExcludes>
      <excludes>
        <exclude>**/target/**</exclude>
      </excludes>
    </fileSet>
  </fileSets>
</assembly>

src

<assembly>
  <id>src</id>
  <formats>
    <format>tar.gz</format>
    <format>tar.bz2</format>
    <format>zip</format>
  </formats>
  <fileSets>
    <fileSet>
      <includes>
        <include>README*</include>
        <include>LICENSE*</include>
        <include>NOTICE*</include>
        <include>pom.xml</include>
      </includes>
      <useDefaultExcludes>true</useDefaultExcludes>
    </fileSet>
    <fileSet>
      <!-- TODO: use expresssions instead: ${project.build.sourceDirectory}, etc -->
      <directory>src</directory>
      <useDefaultExcludes>true</useDefaultExcludes>
    </fileSet>
  </fileSets>
</assembly>