Nope, but there is a decent dictionary style thesaurus at www.m-w.com. I assert that not all word references are created equal. As for reverse dictionaries, the best are still only available on paper, to the best of my knowledge.
If you don't mind letting your fingers do the walking, I would recommend _Roget's International Thesaurus_ (The authentic original and clearly the best; I prefer the 4th edition over the newest 5th for its typography and compact format). Its conceptual organization is superb and the word stock is staggering; far larger than even the OED.
For everyday writing, I find _Sisson's Word and Expression Locator_ to be indispensable (first edition only; the second was re-edited by someone who ravaged the bookís organization). Sisson was the first to successfully put together a true dictionary-style thesaurus (1966). It was a commercial success, so Merriam soon followed with their inferior version in 1972 or thereabouts. Why inferior? A bulkier thesaurus is not necessarily a better one. Sisson's is a slim volume, but oh so exquisitely organized: once you understand it, itís a one stop look up, almost every time. Sisson's is my best kept secret (oops!) I prefer it to all those purportedly handier on-line electronic thesauruses, which I have found a waste of my time. I can more quickly find it in Sisson's. This bookís word stock is remarkably comprehensive, including all those wonderful inkhorn, recondite, and abstruse terms, as well as Latin words and phrases. The first edition is out of print, but very much available at the used book dealers. Iíve seen more copies of it around than of any other edition of thesaurus or dictionary. Itís also quite inexpensive. With these two books, Rogetís International and Sissonís (1st ed), you have all the reverse dictionary you are ever likely to need: a mighty arsenal for the lexiphanicist, and a feast for the verbiphage.