|- src
  |- main
    |- java
      |- ...
    |- resources
|- libs
  |- net
    |- milkbowl
      |- Vault
        |- vault
          |- maven-metadata.xml
          |- ...
          |- 1.2.26-SNAPSHOT
            |- vault-1.2.26-SNAPSHOT.jar
            |- vault-1.2.26-SNAPSHOT.pom
            |- ...
|- pom.xml

<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/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <packaging>pom</packaging>
    [...]
    <repositories>
        <repository>
            <id>bukkit-repo</id>
            <url>http://repo.bukkit.org/content/repositories/snapshots/</url>
        </repository>
        <repository>
            <id>local-dependencies</id>
            <url>file:${project.basedir}/../libs/</url>
        </repository>
    </repositories>

    <dependencies>
        <dependency>
            <groupId>org.bukkit</groupId>
            <artifactId>bukkit</artifactId>
            <version>1.7.5-R0.1-SNAPSHOT</version>
            <type>jar</type>
        </dependency>
        <dependency>
            <groupId>net.milkbowl.vault</groupId>
            <artifactId>vault</artifactId>
            <version>1.2.26-SNAPSHOT</version>
            <scope>provided</scope>
        </dependency>
    </dependencies>
    [...]
</project>

mvn install:install-file -Dfile=/path/to/vault.jar -DgroupId=net.milkbowl.vault
-DartifactId=vault -Dversion=1.2.26-SNAPSHOT -Dpackaging=jar