In forestry a lot of time and effort is spent in forest monitoring and conservation, and until recently there has not been available a successful, economical and easy way to automate this. This implies great importance in sharing the collected data and using it efficiently. Today it is becoming more common to publish the collected data sets from previous studies as the free open source data. Thanks to that data does not have to be collected twice for the same region, and researchers can focus on using the data and developing and testing different models without the need to go onsite, set the experiments and collect the data for years or even longer, which was the case before. This also gives the option of making informed decisions on new regions and testing models before stepping into the multiple year projects or experiments. This study aims to give overview of the free open source data covering global or continental level for use in forestry. Two types of data are described: the primary data and secondary data (derived maps). The biggest biodiversity and biologic collection databases have been selected and described. The brief analysis of the data sources is given and primary sources for future research have been pointed out.