This site has lots of weather links.
Dan,Dan the Weatherman's weather links on his site there is a link to a Belgian site which provides SYNOP data:
Actueel WeerThis page has a clickable image map that when you click on a symbol its definition will show in the lower frame:
Weather Symbols [hint: drag the lower frame border to resize]
Did not find very much on MOS outside of the US. This link has some info from NOAA:
USGOV/NOAA/National Weather Service/MDL/Statistical Modeling Branch Also:
Current NWS MOS Forecast Products 
If I stumble across more links I will post them.