Time and again I read/hear popular-level descriptions of the Higgs mechanism in which it is proclaimed that the Higgs field is "like molasses", offering resistance to particles moving through it. This is an awful analogy, and makes me cringe every time. Even non-physicists should immediately see why: a particle moving through molasses feels a drag force which will ultimately bring it to rest with respect to the molasses (in the absence of some persistent driving force). But the Higgs field fills all of spacetime, and thanks to Galileo and Newton, we know that in empty space, in the absence of forces, particles move with an arbitrary constant velocity (up to the speed limit imposed by Einstein, of course!).
The big difference is that the background value of the Higgs field is Lorentz-invariant — it doesn't define any absolute standard of rest. This is difficult to explain to somebody who doesn't know what a Lorentz transformation is, but it must be possible. Even without knowing mathematics, it is at least plausible that there could be a 'substance' which appears exactly the same to any two observers, regardless of their relative velocity. In fact, this applies to empty space, and it is not unreasonable to say that the value of the Higgs field is just a property of empty space. The problem, of course, is that none of this gives people any idea of what the Higgs field has to do with mass (but in my opinion, neither does the molasses analogy).
So I set a challenge to anybody who happens upon this blog: how does one explain the Higgs mechanism to 'laymen' in a way which is not completely misleading, yet is non-vacuous? Answers in the form of links to good popular-level expositions are perfectly acceptable.
I should acknowledge that at a more technical level, there is a big conceptual difference between the mass of the $W^\pm$ and $Z^0$ bosons, which comes from the true 'Higgs mechanism', and that of the fundamental fermions, which comes from their Yukawa couplings to the Higgs field. This is another level of complexity altogether, and I think it is perfectly okay to leave it out.