[source: NME.com] Green Day's Billie Joe Armstrong has become a volunteer for homeless charity Habitat For Humanity in New Orleans. Armstrong has been posting updates of his work on the band's official website, www.greenday.net. On Thursday April 12 he wrote: "Today we worked on the upper ninth ward. I had to do some upside-down hammering technique but we managed to get the job done. We felt a great sense of accomplishment when we finished." Green Day collaborated with U2 last year on "The Saints Are Coming" to raise funds for Music Rising, an organisation that replaces instruments musicians lost in the wake of Hurricane Katrina.