In this chapter, we provide a general overview of incidence and mortality rates of the most severe cancer types. Further, we provide information about public databases containing valuable resources, for example, expression data or SNP arrays. Due to the complex nature of cancer, we do not limit ourselves to just one cancer type but provide information about a large variety of different cancer types. As motivation for this, we briefly review the Human Disease Network [1,2] focusing on a subnetwork thereof showing a network consisting of different cancer types. Finally, we advocate the usage of the statistical programming language R as a flexible and efficient means to integrate the multilevel sources from different databases with each other.