download.groovy

import java.util.concurrent.ConcurrentLinkedQueue

def results = new XmlSlurper().parse(
        'http://www.howstuffworks.com/podcasts/stuff-you-should-know.rss'.toURL().openStream()
)

ConcurrentLinkedQueue<String> queue = new ConcurrentLinkedQueue<String>()

public void download(String address) {
    new File("downloads/${address.tokenize('/')[-1]}.mp3").withOutputStream { out ->
        out << new URL(address).openStream()
    }
}

results.channel.item.link.each {
    queue.add(it as String)
}

(1..5).each {
    Thread.start {
        String file = queue.poll()
        while (file) {
            println "Downloading ${file}"
            download(file)
            file = queue.poll()
        }
    }
}