HowJSay.com - This is a brilliant web 2.0 tool, just type in a word and get it pronounced immediately. It might prove very useful in some situations. This site has a large database of words so you won’t be disappointed.
Enso Dictionary and Spell Checker - Instantly check the spelling in your text by holding down a hotkey (works universally in Windows). Also included is a dictionary that can be activated using the command ‘define’
Wordie.Org - This is a social network centred around words. You can list your favourite words and phrases, see who else has your favourite word in their list, browse around their lists, tag them and have lots of fun. Create words you hate, words you find weird, words that make you laugh etc. Within a few minutes of wandering on the site, you’ll find lots of new terms that could improve your vocabulary skills.