• Online text to sequence diagram generator: http://www.websequencediagrams.com/
• Online UML diagram generator: http://yuml.me/

Web Services Tools 

• Javascript based webserver using V8: http://nodejs.org/
• Client/Server RPC in Javascript: http://substack.net/posts/85e1bd/DNode-Asynchronous-Remote-Method-Invocation-for-Node-js-and-the-Browser
• Use Javascript in almost any browser to talk to the server: http://socket.io/
• Fast nosql document store: http://code.google.com/p/redis/
• JSON document store with indexing: http://couchdb.apache.org/docs/intro.html