For xxxHolic, you can just download it from thehylia. Season 1-3 is available there, and you can download it for free, however only 3 eps per day
xxxHolic
xxxHolic Kei
xxxHolic Shunmuki - So far, only 2 eps is aired
@edit: Also for a note, it's better to download it with the torrent software, since it gives 5x more speed (as for me, I could download it like 1-1,5mpbs from 300kbps direct download from browser)