based off what you're already reading...

Shaman King: Various groups, currently by manga-rain
Gantz: various groups, currently by shocwave [far batter than the series, actually continues]
Tenjou Tenge: various groups, currently by Evil-Genius [again, vast improvements over the equivalent average series]

Two groups good for browsing: Yanime and AnimeWaves. Good groups with a fairly broad choice of manga.