Are there any sodium salts that are insoluble in water?
From here:


  Sodium tends to form water-soluble compounds, such as halides,
  sulfate, nitrate, carboxylates and carbonates. But examples of many
  insoluble sodium compounds such as sodium bismuthate ($\ce{NaBiO3}$),
  sodium octamolybdate ($\ce{Na2Mo8O25·4H2O}$), sodium thioplatinate
  ($\ce{Na4Pt3S6}$), and sodium uranate ($\ce{Na2UO4}$) is found in
  nature.


Other examples include:


Feldspars(aluminosilicates of sodium, potassium, calcium)
Sodium metaantimonate, $\ce{NaSbO3.7H2O}$ in the pyro form $\ce{Na2H2Sb2O7.H2O}$ has a solubility 0.7g/L.
Sodium metaphosphate, $\ce{NaPO3}$ has both soluble and insoluble form.