Liungman's Symbols Online .

On alchemical symbolism, from Adam Maclean's authoritative alchemy site:

Introduction to alchemical symbolism

For images from mythology, see:

Mythology:  MYTH*ING LINKS' Home Page

For an ancient, worldwide symbol of good luck that the Nazis gave a bad name, visit:
WHY "Gentle Swastika" ?

The Lucky Mojo site sells all sorts of folk magic signs and objects.
 

This site shows Blissymbolics, an attempted universal symbol language invented by C. K. Bliss, and many 
other symbol systems:

BLISS SYMBOL RESOURCES