I just accidentally discovered that in most typing fields in 10.6 or 10.7 (and maybe older as well) that if you hold down Option and hit Delete OS X will delete the last word you typed. If you hold Command and hit Delete it will delete the entire line.
I haven't stumbled across this documented anywhere and it will become part of my keyboarding repertoire. I confirmed it works in iChat, TextEdit, Mail and Safari so I would think it's part of the standard text input library. In MS Word 2008 and 2011 both command and option delete only remove the previous word.
[crarko adds: This is part of the Cocoa text handling system. I found an earlier reference in this hint but it's buried in there and so this particular usage may not be well-known. I trust nobody will be too alarmed if it's pointed out again.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20111013075957110