Hans - A cute, one-minute video about the daily routine of someone's pet woodlouse. This could serve as a great model for a student project that would work well for practicing reflexive verbs.
Science Fi & UFO "Mockumentary" in Italian
Annoying Sister - As told by an elementary student about his sister
You could also ask students to phrase every statement made in the "dubious documentary" in ways that express doubt. For example, "We doubt that . . ., we aren't sure about . . ., etc."
You could also have students make "serious" documentaries such as Ritournelles and Manivelles
Eejit’s Guide to Film-making - This fantastic site contains simple, but comprehensive tips to help amateur movie makers with the pre-, during, and post-production process. The well-designed, nicely illustrated pre-production pages offer suggestions for generating ideas for a movie, laying out a script, structuring the action, and creating storyboards. The other pages include information on costuming, editing, lighting, shooting, and special effects.
Quick 10 Cinematic Errors - A nice article (albeit icky formatting) with 10 Cinematic Errors (for those creating Machinima, but applicable to anything). It will give your students some interesting ideas as well as things to avoid.
Low-tech Alternative: Students can use a National Geographic sort of format in order to accomplish this on paper.