I would recommend Nokia Qt SDK for beginner. It is similar to the SDK of Android / iPhone where you could start a software project , build binary , and deploy on device directly.

However, the emulator do not work for Maemo/N900 , it works only for Symbian simulation.

Maemo SDK is needed when you are going to port software package from other distribution to Maemo, or you want to develop software using language other than C/C++.