Not including games are there really only 4 classes of apps?

1. Fixed content apps

A fixed body of content is displayed in the app. The style of presentation is often very compelling. For example:

The knot app

Pocket Universe

2. Task apps

The app connects to a service either on the phone or in the network that enables it to do something. For example:

A spirit level app

A webcam viewer app                        eg: my webcam

3. Social apps

The users supply the content. For example:

A twitter client

A photo sharing app

4. Combinations of 1,2,3

A combination of classes 1,2 and 3 above. For example; a GPS app that enables you and friends to meet at a McDonalds nearby.