DICTIONARIES

Hypertext Webster Gateway at USCD
Plain text site allows you to enter a word, select an exact or close match, and retrieve a definition.

OneLook Dictionaries
Select from over 570 (!) online dictionaries to search.

THESAURI

Plumb Design's Visual Thesaurus
Java-based interactive database of words and images.

Thesaurus.com
Look up a word, or browse the alphabetical and categorical indexes.

RHYMING DICTIONARIES

Semantic Rhyming Dictionary
10 options for searching for rhymes.

Write Express Online Rhyming Dictionary
Simple interface -- enter a word, it lists the rhymes. You can specify end rhymes, last syllable, first syllable, double or beginning rhymes.

COMBINATION TOOLS

Merriam-Webster Online
Searchable dictionary and thesaurus.

The Wordsmyth English Dictionary-Thesaurus
"A database of relationships between word senses. It organizes English nouns, verbs, adjectives and adverbs into "synonym sets", each such set representing one underlying lexical concept. Different relations link the synonym sets, including relations like "x is a kind of y" (hypernym) and "x has y as a subclass" (hyponym)."