One of the major objectives of systems biology is the development of mathematical models for the quantitative description of complex biological systems, such as living cells. Biological data and software tools for the design, analysis, and simulation of models are two basic ingredients for the new field of systems biology. In this chapter we give an overview of databases and repositories that provide valuable information for the integrative analysis and modeling of data generated by the different omics techniques. We also provide a review of the most popular software tools currently used in computational systems biology studies. Standards for the annotation of biological data and for the analysis and exchange of models are fundamental for the success of systems biology and provide the glue that connects experimental data with mathematical models. We also discuss some broad trends regarding where systems biology is heading to.