The Cook's Thesaurus

I found this site, and I figured it might be helpful for substitutions.  It focuses mainly on US foods substituting US foods, but there are some things that might be of use to those in the UK:

http://www.foodsubs.com/

ETA: I did a search to see if this was posted already and didn't find anything.  If it's a repeat, I apologize. 

That looks really useful! Thanks!!!