I believe such words abound; you'll find plenty enough if you think about it. I guess the way you pronounce words accounts for a lot, as well as the etymological background.

Though, seriously (well, roughly seriously), the "o" spelling was originally based on certain rules:

- When ou before l is pronounced o drop u: mold, sholder. But not sol (for soul).
- When ough is final spell o, u, ock or up, according to the pronunciation: altho, boro, donut, furlo, tho, thoro, thru, hock, hiccup.
- When our is final and ou is pronounced as a short vowel drop u: color, honor, labor http://www.bartelby.org/185/35.html

I suppose the "t" in "thought" means that "ough" is not final.

OK, true. the way the Americans pronounce words can't accounts for much, because they pronounce color in the ame way as we Brits pronounce colour, not the way the Poles say it, for example, which is how they write it (albeit spelled "kolor" in Polish).

Re. #2: OK, the "t" in "thought" means that "ough" is not final, but how about "though"?

I meant that in pronounce, the "ou" is "ow" /aʊ/, but in "colour" it is "uh" /ə/ - we don't say "cull our". Mencken wanted to keep "ou" for "ow" sounds, but change it for "uh" sounds.

In "though" it didn't catch on as well as the others, tho it is a variant: http://www.merriam-webster.com/dictionary/tho

Sorry, CM2DD, Schulter heisst "shoulder" :-)

farfould, click on the link and you'll see those are the original rules proposed by Mencken in 1921. Some caught on, some didn't - e.g. "sholder".