There has been many news stories about the latest release of ubuntu, so it is not a surprise that their site seems very unresponsive. I like kubuntu, so I started downloading a kubuntu torrent. If you have trouble with the main site, I am making the torrent available on mine as well.
For KDE3
kubuntu-8.04-desktop-amd64.iso.torrent
For KDE4
kubuntu-kde4-8.04-desktop-amd64.iso.torrent
Have fun trying them out!