I think Safebooru's still down though (since I visited that more), but I didn't hear of Xbooru ^^'
The place has good fanart, that's for sure. And while Pixiv does have a nice variety as well, some of the fanarts there are a bit more childish, while the ones on 'Booru tend to be a bit more artistic (or, if "childish", it's supposed to be something funny).