1. Native iOS Development
1.1. Requirements
1.1.1. Xcode 4.0, iOS 4.3+
1.1.2. Mobile SDK for iOS
1.2. Skills required
1.2.1. Objective C
1.2.2. REST API
1.2.3. OAuth
2. Native Android Development
2.1. Requirements
2.1.1. Mobile SDK for Android
2.1.2. Java JDK 6, Apache Ant 1.8+, Android SDK v20+
2.1.3. Eclipse 3.6+, Android ADT
2.2. Skills required
2.2.1. Java
2.2.2. REST API
2.2.3. OAuth
3. HTML5 Development
3.1. skills required
3.1.1. HTML5, Javascript,CSS
3.1.2. JQuery, JQuery Mobile
3.1.3. Javascript remoting for Apex controller
3.1.4. Visualforce
3.1.5. OAuth
3.1.6. Web service method (Apex class)
4. Hybrid Development
4.1. Device
4.1.1. forcetk Javascript library wrap a Web app inside Salesforce Mobile Container
4.1.2. Javascript and HTML files stored on the device
4.2. Salesforce Mobile Container
4.2.1. using Visualforce, HTML and Javascript files in server, delivered through native container
4.3. Requirements
4.3.1. Ant 1.8.0+
4.3.2. Git
4.3.3. iOS: Xcode 4.2+
4.3.4. Android: Eclipse Classic, Android SDK r20+, ADT Plugin r20+
4.3.5. Mobile SDK for iOS or Android
4.3.6. PhoneGap
5. Hybrid Development with Mobile Components for Visualforce
5.1. Requirements
5.1.1. Mobile Components for Visualforce
5.2. Skills required
5.2.1. Visualforce
5.2.2. Javascript
5.2.3. JQuery, JQuery Mobile
5.2.4. OAuth
5.3. Disadvantages
5.3.1. Slowest; screens are generated in server side
5.3.2. Cannot leverage native device features, e.g. No notification, cannot access phone's camera, contacts, calendars
5.3.3. Application mostly be online
5.4. Advantages
5.4.1. Standard components already available
5.4.2. No need to use OAuth for authentication
5.4.3. Standard SF Apex objects available
5.4.4. Easier to create and maintain. All knowledge on Visualforce can be leveraged.