We've now lived in the Netherlands for a year, and I've still not found a proper "Cyclists Dismount" sign.
I know what they should look like. the Dutch equivalent is "Fietsers Afstappen", and I have plenty of experience of encountering these things from cycling in the UK so I know what I'm looking for. However, they appear to be a theoretical possibility rather than a reality.
All I've found so far have been temporary signs erected around roadworks, and cyclists are (quite reasonably) asked to dismount here for the market which completely fills the street. However, I've not ever seen a permanent sign.
At the start of the 2006 Study Tour I offered €10 to the first person to spot a sign which read "Fietsers Afstappen", knowing that even though we were going to places where I'd never cycled before, there was very little chance of finding such a sign. I kept my money.
These signs can be seen as a bit of a joke, but they're much worse than that for cyclists. The problem is that each time you slow down and stop you lose a lot of momentum. It's like increasing your journey length by several hundred metres. This is why direct and uninterrupted cycle routes are such a good idea. Luckily, the planners here provide exactly that.
Of course it's not just important for commuters that routes should be convenient. It also makes cycling holidays far more relaxing and enjoyable.
The photo was taken in Cambridge near where I used to live. At one time I had a plan to try to take photos of all such interruptions for cyclists), but I quickly realised this was an infeasibly big undertaking and the web page where the project started languishes out there in "cyberspace"...
The best photo of cyclists dismount signs that I've seen is to be found on Warrington Cycling Campaign's wonderful "facility of the month" website. The Netherlands can't begin to compete with that...
At the end of this you may be wondering what happens in the Netherlands to avoid this problem. Try looking at these examples of making cycle routes direct.
(Sorry about no picture of a genuine "Fietsers Afstappen" sign to accompany the above. I've not been able to find one...)
Update 2010: I found one at last, built new here in Assen. There are extenuating circumstances...