Phase II is fan fiction based on the original Star Trek, characters, and sets (with some graphics modernization). These are hour long episodes and are surprisingly good; the acting is at least as good as the original series and they have significantly better special effects.
You can download the episodes from their webpage: Star Trek: Phase II, Episodes
The first one I watched was Episode 6: "Enemy Starfleet"
and is available on You Tube, however finding the rest of them in their entirety is tricky (many are split into segments). It was quite well done and has sold me on watching more of them.