Spell Check lists the correct spellings and syllabications of the working vocabulary of Standard English. The book includes a variety of challenging words in fields ranging from science and technology (amyloid, blogosphere) to contemporary culture (feng shui, sudoku).
Kind of embarrassing to admit, but I probably use this little book twice a week. It's very user friendly and does seem to contain just about every word I habitually misspell. Its only flaw is that I think it could be a bit longer, but I guess that would interfere with how convenient it is to use.