For posting:
If you just want to get a video clip online and share it with friends via email or on your own blog, Vimeo wins for its speed, ease-of-use, and simple playback functions. It also lets users download the original file, and features some light community features. An alternate choice is Video Egg

For viewership:
If you want to step up to more community features and get widespread viewership of your viral clip, Youtube gets the job done with a lot less hassle than VSocial or Grouper

For editing:
If you want to alter your video online in any way--through editing, remixing, or combining your clips with those from other users--then head on over to Jump Cut and don't look back. This site really offers the first leap forward in online video sharing, and its worth a look even if you have no use for editing features.  There is other alternate choice on the market yet although Motionbox looks to be a potential competitor.