So I wanted to manage Ethereum accounts in browser: generation, management, everything. So I made this module to do just that. This module is not completely secure yet and should not be used in production. It's largely a development module at this point. I understand that Fabian (frozeman) has made a similar module for managing Ethereum accounts. This module covers more the generation and signing of Ethereum accounts in browser. As well, you can optionally choose to override the web3 object so that if the sendTransaction (or contract transaction) method is used with an in browser account, it will intervene and build/sign the transaction in browser and leverage the sendRawTransaction method to send the data to the node.
The module is available in a Meteor package, NPM package and as a single, stand alone JS file. If you're using this module in a Meteor project, the storage is reactive (thanks to Fabian's LocalStore module). This module uses the browsers persistent localStore storage, and Chromes custom localStore (if Chrome is used).
Hope this helps!