Spreadthesign is a site for learning sign languages:
Here you will find an international dictionary of the following national sign languages: Swedish, English (BSL), American English (ASL), German, French, Spanish, Portuguese, Russian, Estonian, Lithuanian, Icelandic, Latvian, Polish, Czech, Japanese, Turkish. American Sign Language and baby signs are also included in this dictionary.
This webpage is administered by the Non-Governmental and Non-Profit Organization European Sign Language Centre. Though the primary objective of the Centre is to make national sign languages available to people with hearing disabilities, the overall ambition is to make sign languages accessible to everyone.
You type a word into the search box and you’re presented with a group of flags; pick one, and you’ll see a user of the relevant sign language demonstrating it. I input “cat” and learned that most sign languages seem to identify it by its whiskers — but Ukrainian has one hand scratching the other, and Turkish has a similar gesture but with more of a soft petting motion. I wrote irritably to Yoram, who sent me the link (thanks, Yoram!), that “they expect you to know all the flags,” but I was too hasty; if you hover over the flag, you see the identification in a popup. A nice site.