Ninjawords
Speaking of words I like, I found the online dictionary Ninjawords in 2006 when I discovered Wordie, the social network for pedants and grammarians. Ninjawords has since become my favorite general-purpose online dictionary. (At school, I use the OED when I want to see some etymology.) Ninjawords is light on features, which itself is its greatest feature next to its speed. I personally like the lookup history, which makes it easy to see what words you’ve looked up recently. Great for, among other things, reinforcement when learning new words.