I recently created a web based tool that allows you to manage your private data and generate passwords safely. If you are interested in trying it click here.
I suspect that it will only work on newer browsers. I have only tested it on Firefox 15, IE 9 and Chrome 23. See the tool help for more detailed information.
I wrote it because I have been doing password management using a variety of local tools for many years. I blogged about one of the tools: seced sometime last year. It was platform independent (python) but could not access remote data, required python and had to be installed on each host. Other tools like Microsoft Excel also worked but were limited to a single OS. In other words, none of these solutions worked for my tablets or smart phones.
This tool works on any web enabled platform. It does all computation locally with no server interaction which means that you can read encrypted information stored in JSONP format on a remote site and decrypt it locally relatively securely.
I say relatively secure because MITM (man in the middle) attacks would be able to grab your encrypted data and perform a rainbow attack which means that if you have a weak password, your data will not be secure. In addition your data is vulnerable to social engineering, screen capture and key logging attacks but that is the same level of vulnerability that local tools have.
You an also generate JSONP data for use by this tool but because of cross-site domain access restrictions this tool cannot write data so you need to generate it and then cut-n-paste it into a file.
I built it using the crypto-js library (http://code.google.com/p/crypto-js/) and the HTML5 boilerplate library from http://html5boilerplate.com/. I also made extensive use of jquery and jquery-ui. All of those projects deserve your support.