Houghton Mifflin Roget's II: The New Thesaurus, 3rd Edition, Hardcover, 1216 pages (0618254145)
Organized alphabetically.
Synonyms, antonyms, usage.

Webster's New College Dictionary, Third Edition
Family-friendly volume features more than 200,000 clear, concise definitions.
Biographical and geographical entries have been completely updated, reflecting current events and the latest census.
Includes over 400 updated line drawings.
Other features include redesigned tables for world alphabets, bible, calendar, currency, elements, geologic time and measurement.
Thumb-indexed.

The American Heritage Dictionary of the English Language, Fifth Edition
400,000 entries with 10,000 new words and tenses.
Full-color with 4,000 photographs and illustrations.
Updated guidance on usage from the renowned America Heritage Usage Panel, and new notes on regionalisms and language variation and change.
New notes on regionalisms and language variation and change.
Thousands of updated etymologies, a fully revised Appendix of Indo-European Roots, and a new Appendix of Semitic Roots.