Here are some useful Maven2 Repositorys listed.
EclipseLink:
<repository>
<id>EclipseLink Repo</id>
<url>http://www.eclipse.org/downloads/download.php?r=1&nf=1&file=/rt/eclipselink/maven.repo</url>
</repository>
PLOIN Repository, containing ploinFaces and ploinMailFacotry:
<repository>
<id>ploinPublic</id>
<name>ploinPublic</name>
<url>http://ploin-m2.de/nexus/content/groups/public/</url>
</repository>
JSF 2.0, java.net:
<repository>
<id>maven2-repository.dev.java.net</id>
<name>Java.net Repository for Maven 2</name>
<url>http://download.java.net/maven/2/</url>
<layout>default</layout>
</repository>
Ibiblio, mirror of M2:
<repository>
<id>ibiblio.org</id>
<name>ibiblio Repository for Maven 2</name>
<url>http://mirrors.ibiblio.org/pub/mirrors/maven2/</url>
<layout>default</layout>
</repository>
Codehaus
<repository>
<id>repository.codehaus.org</id>
<name>Codehaus Repository</name>
<url>http://repository.codehaus.org/</url>
</repository>
Selenium:
<repository>
<id>openqa-releases</id>
<name>OpenQA Releases</name>
<url>http://archiva.openqa.org/repository/releases/</url>
<releases>
<enabled>true</enabled>
</releases>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
<repository>
<id>openqa-snapshots</id>
<name>OpenQA Snapshots</name>
<url>http://archiva.openqa.org/repository/snapshots/</url>
<releases>
<enabled>false</enabled>
</releases>
<snapshots>
<enabled>true</enabled>
</snapshots>
</repository>
<repository>
<id>openqa-thirdparty</id>
<name>OpenQA Third Party</name>
<url>http://archiva.openqa.org/repository/thirdparty/</url>
<releases>
<enabled>true</enabled>
</releases>
<snapshots>
<enabled>false</enabled>
</snapshots>
</repository>
Spring-Framework:
<repository>
<id>springsource maven repo</id>
<name>springsource maven repo</name>
<url>http://maven.springframework.org/milestone</url>
</repository>
JBoss:
<repository>
<id>repository.jboss.org</id>
<name>Jboss Repository for Maven</name>
<url>http://repository.jboss.org/maven2/</url>
</repository>
<repository>
<id>snapshots.jboss.org</id>
<name>Jboss Snapshots Repository for Maven</name>
<url>http://snapshots.jboss.org/maven2/</url>
<snapshots>
</snapshots>
</repository>