sproutcore
SproutCore has gotten a lot of attention lately, with the news that MobileMe will be very heavy with it. I took it for a spin and i do like it, mostly because it reminds me so much of Cocoa. By design i hear. I think the project is young and very promising, and if Apple can throw it's weight behind it then there's a key player that thinks so too.
i think something like SproutCore can prove to be an easy transition area for web developers like myself into Cocoa, as so much of the key concepts are there. MVC, KVO, etc. It also makes it easy for me to learn sc, since i've been into Cocoa for 2 years now. all of a sudden my job of web developer and hobby/passion of Cocoa development are converging, and i couldn't be happier
i plan on posting my amazing work here and expanding on the example. if it turns out to be anything worth documenting, i'll blog about it. need to make time for it though!