Anime Domein - another searchable database with a section for fan art. Several round robin comics of various genres are available for you to sign up. Impromanga - Several round robin comics of various genres are here for you to sign up for.
Finished comics are here as well.
Monthly Online Manga - a contest where you develop a short comic based on one of two themes. Special guests included Robert DeJesus and Locke. Opening its 56th convention. California, July 16 - 18, 1999. Special guests include Akira Kamiya, more will be confirmed.