I'm going to start off with one that I came across recently:
In English, this translates literally to something like "It's like I met a merciful person in hell" (though 仏 can also mean "Buddha").
I think this is a pretty good English version of the meaning behind it: "In my hour of true need I found a true friend."
Though I'm not exactly sure a "true friend" is what's meant here. What comes to mind for me is the story of the good Samaritan. The guy that had the crap beaten out of him was in his hour of need, and someone merciful came upon him and helped him. I think that situation would probably be an ideal use for this proverb.