This past weekend, I particpated in Memphis's 48 Hour Launch. It's a weekend-long event where anyone can pitch a business or app idea on a Friday night, try to get enough people to buy into the idea, and form your team. Then, you spend the weekend building something, and on Sunday you get a chance to showcase what you've accomplished.
I was fortunate enough to team up with a few friends (and some new ones!) to build an intial version of Happy Potty: A mobile app that helps you find a clean place to... go. Check it out! It's not quite available yet, but once it is, we hope you'll have fun using it. Once it's ready, we'll start talking about it on twiter (via @happypotty).
I know it's nothing new, per se, but this was completely new to me; I've not really done any mobile work, but PhoneGap really does make prototyping a mobile app increadibly easy. You get access to a lot of the device's internals, while using tools that are second nature to any seasoned web developer.
I'm sure there are some caveats here, but if you want a working prototype for simple mobile app, definitely give PhoneGap a spin.
I really like jQuery, and I've known of jQuery Mobile's existance for quite some time, but again, I'd never played with it. I did run into a few quirks regarding the timing of events (when is my code executing vs. jQuery mobile), but all-in-all, this is a really nice toolchain.
There's also, codiqa which I'd totally pay for if I spent much time at all building mobile apps. It's a really nice drag & drop interface builder using jQuery mobile's widgets.
We weren't using Backbone.js on this project, but it appears that Parse plays pretty nicely there, too.
I'd always toyed around with the idea of getting into mobile app development, but had never jumped headlong into the fray. I didn't realize just how accessible these tools are to web developers.