md5.js
Node style md5 on pure JavaScript.
From NIST SP 800-131A: md5 is no longer acceptable where collision resistance is required such as digital signatures.
Example
var MD5 = require('md5.js')
console.log(new MD5().update('42').digest('hex'))
// => a1d0c6e83f027327d8461063f4ac58a6
var md5stream = new MD5()
md5stream.end('42')
console.log(md5stream.read().toString('hex'))
// => a1d0c6e83f027327d8461063f4ac58a6