Labio-dentals in Dutch

Dutch is unique (no, it's not!) in having three different labio-dental sounds, which differ only in their degree of voicedness vs. friction:
voiceless f, voiced v (not very voiced, but more than f), and very voiced approximant w.

The three-fold distinction is not present throughout the areas where Dutch is spoken (the Netherlands and roughly half of Belgium): In some people's speech, f and v are very similar, of even identical, leaving a normal two-fold distinction f/w, like in German, and in many Slavic languages.

Others do distinguish between f and v, but use a w that is bilabial (pronounced using both lips), not labio-dental (using upper teeth and lower lip). This happens notably in southern parts of the Netherlands (provinces Noord-Brabant and Limburg) and in Dutch-speaking Belgium.

These two types of reduction from three-fold to two-fold distinction(s) do not coincide geographically, and that leaves speakers - and I happen to be one myself - who distinguish f, v and w, all three being pronounced with lower lip and upper teeth, only through the balance between voice and friction.

Three-fold minimal "pairs" are hard to find, and those that do exist invariably involve a loan word or acronym or some other special case. Here is a list of what I could find:

faal vaal waal
faas vaas waas
FAL val wal
falen vale walen
fat vat wat
fatten vatten watten
fasen vazen wazen
fee vee wee
feest veest weest
feil vijl wijl
fel vel wel
felle vellen wellen
FET vet wet
fezel vezel wezel
fier vier wier
fis vies wies
Fin vin win
fit vit wit
fitte vitte witte ( *)
fitter vitter witter
fitters vitters witters
font vond wond
fout voud woud
fort vort wort

A word with all three sounds in it: verfwerk.

See also this link about the distinction between voiced and voiceless fricatives in Dutch.

And here is a sound sample of how I pronounce two of these trios:
Sounds sample (in au-format):
Fier, vier, wier; faal, vaal, waal

Addition 16 April 2011: Other people have written about this subject (in Dutch), long ago and more scientifically than I did.

References:

A discussion in usenet group nl.taal, which made me aware of this fact.
Cor van Bree, Historische Grammatica van het Nederlands, Foris Publications, Dordrecht 1987
C.B. van Haeringen in De Nieuwe Taalgids, Jaargang 37. J.B. Wolters, Groningen / Batavia 1943