For many startups I've seen relatively simple videos which describe the web application. I want to create a little 1 minute video to show what our product has to offer.
Some examples what I mean:
http://www.youtube.com/watch?v=1BbK9o5fQD4&feature=player_embedded#!
http://www.youtube.com/watch?v=5wx0GfbC0BA&feature=player_embedded
They are both done by the Epipheo Studios but would think that there is some awesome software to create most of the effects.
