This website is part of the Envato network (the guys who bring you themeforest and graphicriver) and is a really good design & development resource.
Drioideo is a website as the name suggests for videos on Android. Here you can find videos related to unboxing, sneak peak at new app/feature demos, phone hardware and more.
This is the sister site of AppVee iPhone app reviews and apart from reviewing Android Apps, they also offer YouTube video screencasts.
Introduction to Apple iOS App Development
Apple's official into module is a simple step-by-step guide to all a developer needs to know about developing an iOS app.
Android Guys is blog that covers everything you wanted to know about Android - news, reviews, interviews, Podcasts, etc.
This site offers a monthly subscription to really good courses that take you from a beginner to a pro level.
Tutorialspoint – iOS Application Development
Tutorialspoint has a really good course on developing iOS app and caters to both beginner devs as well as those with experience.
Jay Freeman has created an extract of the App Market. The browser features comments, user ratings, app descriptions, and more.
Android Tapp is a good resource for App Reviews and Ratings, interviews with developers and news
Talk Android has a forum which contributes to a huge number of Android Wallpapers
Livecrunch is a Tech blog that gives a lot of attention to the Android OS, news and devices. Their motto is to "keep it simple stupid"
This one is a blog that contains free tutorials and guides for mobile development as well as comprehensive learning programs that can be purchased.
iOS Dev Center
This resource is only accessible to paid members of Apple's Developer Program and is the official iOS Dev Center.
This is a forum and a really good place to ask questions and get answers from the community. Apart from app development, the forum also focuses on app marketing.
Phandroid is an Android blog covering all things Android including breaking news, insights and reviews. They also own a forum called Android Forums.
This is a really good blog for iOS devs focused especially on game development.
T-Mobile G1 (Android) forum
T-Mobil's Official forum for all General Discussion and Feedback, discussion, praise and gripes.