JBoss's Maven Repository is at: http://repository.jboss.org/nexus/content/groups/public/

Here's the pom.xml fragment to use. RESTEasy is modularized into various components. Mix and max as you see fit. Please replace 3.9.1.Final with the current RESTEasy version you want to use.

<repositories>
   <repository>
      <id>jboss</id>
      <url>http://repository.jboss.org/nexus/content/groups/public/</url>
   </repository>
</repositories>
<dependencies>
   <!-- core library -->
   <dependency>
      <groupId>org.jboss.resteasy</groupId>
      <artifactId>resteasy-jaxrs</artifactId>
      <version>3.9.1.Final</version>
   </dependency>
   <dependency>
      <groupId>org.jboss.resteasy</groupId>
      <artifactId>resteasy-client</artifactId>
      <version>3.9.1.Final</version>
   </dependency>

   <!-- optional modules -->

   <!-- JAXB support -->
   <dependency>
      <groupId>org.jboss.resteasy</groupId>
      <artifactId>resteasy-jaxb-provider</artifactId>
      <version>3.9.1.Final</version>
   </dependency>
   <!-- multipart/form-data and multipart/mixed support -->
   <dependency>
      <groupId>org.jboss.resteasy</groupId>
      <artifactId>resteasy-multipart-provider</artifactId>
      <version>3.9.1.Final</version>
   </dependency>
   <!-- RESTEasy Server Cache -->
   <dependency>
      <groupId>org.jboss.resteasy</groupId>
      <artifactId>resteasy-cache-core</artifactId>
      <version>3.9.1.Final</version>
   </dependency>
   <!-- Ruby YAML support -->
   <dependency>
      <groupId>org.jboss.resteasy</groupId>
      <artifactId>resteasy-yaml-provider</artifactId>
      <version>3.9.1.Final</version>
   </dependency>
   <!-- JAXB + Atom support -->
   <dependency>
      <groupId>org.jboss.resteasy</groupId>
      <artifactId>resteasy-atom-provider</artifactId>
      <version>3.9.1.Final</version>
   </dependency>
   <!-- Spring integration -->
   <dependency>
      <groupId>org.jboss.resteasy</groupId>
      <artifactId>resteasy-spring</artifactId>
      <version>3.9.1.Final</version>
   </dependency>
   <!-- Guice integration -->
   <dependency>
      <groupId>org.jboss.resteasy</groupId>
      <artifactId>resteasy-guice</artifactId>
      <version>3.9.1.Final</version>
   </dependency>

   <!-- Asynchronous HTTP support with Servlet 3.0  -->
   <dependency>
      <groupId>org.jboss.resteasy</groupId>
      <artifactId>async-http-servlet-3.0</artifactId>
      <version>3.9.1.Final</version>
   </dependency>

</dependencies>

There is also a pom that can be imported so the versions of the individual modules do not have to be specified. Note that maven 2.0.9 is required for this.

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.jboss.resteasy</groupId>
                <artifactId>resteasy-bom</artifactId>
                <version>3.9.1.Final</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>