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The difference between utf8_general_ci, utf8_unicode_ci & utf8_bin

I found this very interesting question at stackoverflow:

What are the diffrences between utf8_general_ci and utf8_unicode_ci?

utf8_general_ci is a very simple collation. What it does - it just - removes all accents - then converts to upper case

utf8_unicode_ci supports so called expansions and ligatures, for example: German letter ß (U+00DF LETTER SHARP S) is sorted near "ss" Letter Œ (U+0152 LATIN CAPITAL LIGATURE OE) is sorted near "OE".
utf8_general_ci does not support expansions/ligatures, it sorts all these letters as single characters, and sometimes in a wrong order.

utf8_unicode_ci is generally more accurate for all scripts. For example, on Cyrillic block: utf8_unicode_ci is fine for all these languages: Russian, Bulgarian, Belarusian, Macedonian, Serbian, and Ukrainian. While utf8_general_ci is fine only for Russian and Bulgarian subset of Cyrillic. Extra letters used in Belarusian, Macedonian, Serbian, and Ukrainian are sorted not well.
The disadvantage of utf8_unicode_ci is that it is a little bit slower than utf8_general_ci.

So when you need better sorting order - use utf8_unicode_ci, and when you utterly interested in performance - use utf8_general_ci.

Source: http://forums.mysql.com/read.php?103,187048,188748#msg-188748

Source: http://stackoverflow.com/questions/1036454/what-are-the-diffrences-between-utf8-general-ci-and-utf8-unicode-ci

Additional I can say: utf8_bin is case-sensitive because it's binary!