The one I'm trying to do most recently is to compile bitcoin's bx[1] to wasm, so it can be run in the browser. It's not a crypto-related project, I primarily need the mnemonic generation code so I can generate mnemonics from passphrases for more general-purpose reasons.
Two reasons I'm thinking of getting it done in WASM: First is of course, not to roll my own crypto. Second is that if you're asking someone to generate a private key to use themselves, sending ANY information to a server is a big no.
Honestly I'd appreciate any thoughts or advice anyone has, I'm open!