I do not have a good resource, however, I know a few off the top of my head: 1) characters with modifiers, like umlauts, sometimes collate the same, and sometimes collate differently; 2) multiple characters may collate as a single character, such as "ll" (I just did a search to verify that this was the case in Spanish, and found the Collation page on Wikipedia, which you might find interesting); and 3) different locales may choose to collate numbers using different algorithms (in English we usually expect "1,000" to sort after "200", but if "," is a decimal point, then you might not).