Just added a new timelapse movie to vimeo, with clips taken in the Provence and at the Côte d'Azur in France. Most shots were taken using a Hoya ND400 (Neutral Density) filter, allowing exposure times of seconds instead of below 1/100s or so. The result is a very smooth timelapse movie.
The drawback is that the ND400 is not a very neutral filter (neutral would mean that every wavelength (=color) is attenuated by the same amount) and color correction needs to be applied in post production. I managed this by using a rather cool white balance around 3000-4000K depending on the amount of clouds.
Here is the resulting movie: