In the last decay, many mobile development platforms are emerging for the implementation of mobile services in the markets. These development platforms are offered by industrial giants such as Microsoft and Apple to enable the mobile service development for the third party. Some of them are Symbian Operating System from Nokia, Blackberry Operating System from RIM, iPhone Operating System from Apple Inc., Windows Mobile from Microsoft, Java ME from Sun, the open-source embedded Linux, Android Operating System from Google, and BREW from Qualcomm. In this chapter, we comprehensively describe these development platforms and these open development environments. For each of the platform, the main features will be summarized including the operating system itself and the corresponding development tools. Some mobile services developed by using these platforms are also illustrated as examples. Some comparative studies such as advantages and disadvantages of the platforms are further presented.