Rich Internet Applications: They're Great! But Not Enough

The Rush to the Web is really amazing. Google Apps, gadgets, Yahoo pipes, and a plethora of RIA (Rich Internet Apps) technologies are making great strides in making the Web experience as rich and powerful as native, local applications. This is great if you live in technology metro-centers where you always have a connection. Without a connection, you are out of luck. There are a few people out there making the Web experience work offline...which begs the question: If I'm working offline, why am I using Web apps? There are many good reasons to do this, for me the most important is seamless user experience: there is little visible difference from working online vs. offline other than the obvious lack of connection.

Still, there is the contrarian curmudgeon in me that says there is something amiss with this. And, as a P2P practitioner there is another model. Smart apps for the local machine / OS...or Java, etc., if you want cross platform. Why not use the power of the local application environment with all the look and feel comfort of the local OS not to mention the computing power of the local machine. I have a tough time making this case for Windows, but it certainly works for UNIX, Linux, BSD and most especially for the Mac. I mean, I paid top dollar for the Mac experience and now I'm limited to what I can run in Safari? Not enough, thanks.

My Macs, combined with a .Mac account provide what I need and want to use. What I want is an easy way (dev tool) to mash-up (and consume, process, apply logic, etc.) data from various sources across the Web and my local machine / machines on network (ala Bonjour) using an easy-to-create native UI toolset for Mac OS X. 

The closest thing I've found to gather the data is RSSBus Desktop. Unfortunately, it is .Net centric. It also doesn't offer a native UI builder either, which is what I want...for the Mac.

A prime example of a rich local application that works connected or not is iTunes. Many Widgets in OS X work the same way. I can build my own special client-side apps using Xcode but that is more heavyweight ( a real programming IDE ) than what I want and need for simple apps. So, how do you build local client UI applications for Mac OS X without Xcode that can mashup data sources using a lightweight Web 2.0 toolset approach? If you know of any tools (preferably open source!) please let me know!

Web 2.0 web-based rich Internet applications hosted on remote servers are fine and valuable but I also want something richer and more native to my Mac that takes advantage of my investment in my local machines. I want it all!