If you are building a Java project that has Hadoop or HBase dependency  (for example a Java mapreduce application), here is a simple POM.xml to get you started
1) project structure:
pom.xml
src/main/java  <--- all the java code goes here
2) POM.XML
here is the pom.xml on github : https://gist.github.com/sujee/7916669
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>mygroup</groupId> <!-- change this -->
<artifactId>project_name</artifactId> <!-- change this -->
<packaging>jar</packaging>
<version>1.0</version>
<name>Sample Project Name</name> <!-- change this -->
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>2.3.2</version>
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-core</artifactId>
<version>1.2.1</version>
<exclusions>
<exclusion>
<groupId>org.codehaus.jackson</groupId>
<artifactId>jackson-core-asl</artifactId>
</exclusion>
</exclusions>
</dependency>
<dependency>
<groupId>org.apache.hadoop</groupId>
<artifactId>hadoop-test</artifactId>
<version>1.2.1</version>
</dependency>
<dependency>
<groupId>org.apache.hbase</groupId>
<artifactId>hbase</artifactId>
<version>0.90.2</version>
</dependency>
</dependencies>
</project>
3) Compiling
To compile
$ mvn compile
to create jar
$ mvn package
This will create a jar file in target/ directory
4) Adding more dependencies
You can search and add dependencies from http://mvnrepository.com/
