These are sites which feature complete works of fantasy and/or science fiction on a regular basis, but with an irregular table of contents. Most rotate their material on a monthly basis. Any number of sites rotate excerpts of larger works, and those may be found in the Chapters and Excerpts listing.
Mind's Eye Fiction publishes some quality stories, but be aware that they usually charge you some money to finish reading them!
Omni Magazine is dead, alas, but Ellen Datlow and crew created Event Horizon as an online pub, where she continues her role as one of sf's best editors.