The Comprehensive LaTeX Symbol List (from CTAN)
LaTeX Symbols
Table: Text-Mode Accents
Table: National Symbols
Table: Miscellaneous Symbols
Table: Math-Mode Accents
Table: Greek Letters (Math Mode)
Table: Binary Operations (Math Mode)
Table: Relations (Math Mode)
Table: Variable-Sized Symbols (Math Mode)
Table: Delimiters (Math Mode)
Table: Function Names (Math Mode)
Table: Arrows (Math Mode)
Table: Miscellaneous Symbols (Math Mode)