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Adobe has just shipped Bickham Script Pro in three weights. To the best of their knowledge, this represents the most complex and sophisticated use of contextual rules for alternates and ligatures in an OpenType font to date. Many lowercase letters have 20-30 alternate forms. The "th" ligature alone comes in 9 different versions. Contexts even cross words, resulting in interesting effects like as many as four different versions of the word "the" depending on context. (There may be more, but I was only able to figure out how to get four so far.)
The package can be found at the Adobe Type store by following this link: http://store.adobe.com/type/browser/F/BIPQ/F_BIPQ-10005000.jhtml
To view the glyph complement with all the alternates and the rest of the goodies, follow this link: http://store.adobe.com/type/browser/pdfs/BIPQ/BickhamScriptPro-Regular.pdf (304K PDF)