Hi Tor,
here is what my AOM (737-31S) says (i don't know if that's boeings procedure though):
2.8.53
Crosswind Landing
Two methods of performing crosswind landings are presented. There is the de-crab technique (with removal of the crab during the flare) and the crab technique. During crosswind conditions, the crosswind wind correction angle can be maintained to touchdown. From the pilots perspective the flight deck will be offset from the centerline when the main gear touches down on the runway centerline.
2.8.54 Crossind Landing Capability
Boeing demonstrations of crosswind capability were performed using normal landing configuration on dry runways all engines operating, and with one engine out. The resulting crosswind guidelines are shown in the table below:
Dry: 40kts crosswind (reduced in our OPS to 35kts)
Wet: 25kts crosswind
Contaminated/Degraded Braking: 15kts crosswind.
Reduce crosswind guidelines by 5 knots on wet and contaminated runways whenever asymetric thrust is used.
Crossind limitation are found in Part B chapter 1.1
Wind is measured at 10 metre tower height.
Landing on untreated ice should only be attempted when no melting is present.
The crosswind guidelines shown in the table above through analysis and piloted simulation evaluations. These crosswind guidelines are based on steady wind (no gust) conditions. Due to the difficulty in modelling gust magnitude, duration, frequency and direction, gust additive to these guidelines is not provided.
2.8.55 De-Crab during flare
The objective of this technique is to maintain wings level throughout the approach, flare, and touchdown though aligning the longitudinal axis of the aircraft with the runway. On final approach, a crab is established with wings level to maintain the desired course. Just prior to touchdown while flaring the aeroplane, downwind rudder is applied to eliminate the crab and align the aeroplane with the runway centerline.
As rudder is applied, the upwind wing will sweep forward, developing roll. Hold wings level with simultaneous application of aileron control into the wind. The touchdown is made with cross controls and both gear touching simultaneously. Throughout the touchdown phase upwind aileron is utilized to keep wings leve.
2.8.56 Crab
On very slippery runways the crosswind crab angle may be maintained to touchdown. This will reduce drift toward the downwind side when touching down. Since the aircraft does not have to be decrabbed, pilot workload is reduced. Proper rudder and upwind aileron must be maintained to ensure directional control is maintained.
On slippery runways, crosswind capability is a function of runway surface conditions, aeroplane loading and pilot technique.
The aeroplane can land using crab only (zero side slip) up to the landing crosswind guidelines in the table on the previous page.
That's all about crosswind landings in the AOM. You can even use the wing-down technique in moderate crosswind (up to 9° of bank at around 5° pitch up).