How to Add a Thesaurus in LibreOffice (OpenOffice)

I just started using LibreOffice 3.3.3 and am astounded to learn that there isn't a working thesaurus.  At least not for English (UK) or English (Canada).  The Thesaurus menu option is greyed out when using either of these languages, and CTRL + F7 doesn't do a thing.

Some Googling brought me to the Weekly Whinge and a UK language thesaurus extension.  It looks like it's old (March 2009) but it works great.  Just install via Tools > Extensions Manager and you are good to go.