I needed the LaTeX code for the sign that is called the "promille" sign in Dutch. It's the sign like the percent sign "%" ("procent" in Dutch), but with two circles at the bottom. Googling for "latex promille" was not very successful, so I thought this would be a good botsnack. (Googling for "permille" or "(parts) per thousand", yield better results however.)
Anyway, I found two solutions:
\textperthousandfrom the package
textcomp, also provides
\textpertenthousandbut both only work in text mode, not in math mode.
\permilfrom the package
wasysym, works in both text mode as in math mode.
That's all folks