First of all, let me mention what is indisputably
the finest tool that any writer with a computer can have: The
Oxford English Dictionary, on CD-ROM for Windows. This is the
full, no-holds-barred edition and worth every single penny. I wouldn't
be without it now but - be warned - you can spend forever simply exploring
it. It's a marvellous thing to read in its own right. If you love
words, you should not be without this.
Defining over half a million words, the 2nd edition of this exhaustive
guide to the meaning, pronunciation and history of words is now available
on CD-ROM. It allows easy browsing for casual use, searching on phonetic
spellings, complex searching using a specially-designed language,
and the ability to save and combine results.
More information on the O.E.D.
website (but buy it from Amazon
- it's cheaper!).