I can't even remember why I started pursuing this train of thought, but (if you speak Japanese) check out this neat page about Osaka sign language.

Immediate fun: fingerspell something in yubimoji (指文字). (Osaka yubimoji seem to be the same as the standard JSL [= Tokyo] version.)

There are also interesting sections about Osaka place names, and a table showing the differences between Osaka and Tokyo signs for common words.

SORRY (gomen nasai)

OSAKA: Touch your chin with the end of your thumb and fold your other four fingers into a ko shape (コ) while lowering your head slightly.
　
TOKYO: Pinch the area between your eyebrows with the thumb and forefinger of your right hand, then straighten your right hand and bring it forward and down from your brow.

"Sorry I did something that made you wrinkle your brow in frustration or worry", is apparently the etymology for that last one.

For English speakers: this palimpsesty collection of lectures and e-mails about ASL grammar is interesting too.