Geodata is very important for those who is working in geospatial world. In map making process or spatial analysis, data is a prerequisite to get the job done. The problem is, not all data that we need are available. This post will review some resources to get geodata for free (open geodata). This post will be updated as new resources found. If you have other resources please let us know via email in contact page or post it in comment area at the end of this post. Happy reading.
USGS earth explorer is a service from United States of Geological Survey (USGS). We can find many data with numerous themes, resolutions and sensors like satellite imagery, Lidar, weather, Radar, landcover, etc. Mainly the available data has full coverage for United States area, but global coverage data also available for example Digital Elevation Model (DEM) data from Shuttle Radar Topographic Mission (SRTM), Landsat satellite imagery, vegetation monitoring and so on.
USGS Earth Explorer
Figure 1. USGS Earth Explorer
Climate data in geospatial format is hard to find especially for global coverage. For you who need the climate data, worlclim could be a good resource. Worldclim provides climate data such as temperature and precipitation both annual and monthly. The data was compiled from weather stations all over the world in 1960-1990 for dataset version 1.4 and in 1970-2000 for version 2. Worldclim also provides prediction of current climate, past and future. The data can be downloaded in raster format with 1 km resolution.

Worldclim Data
Figure 2. Worldclim Data
Ina Geoportal is an Indonesian official opengeodata. It is managed and  maintained by Badan Informasi Geospatial (Geospatial Information Agency) which is responsible for provision geospatial data at national level in Indonesia. In InaGeoportal, a user can download topographic data in scale 250K, 50K and 25K. To get the data is very easy, we just need to fill a form with name, email, kind of data and user category. Of course we have to agree with the term and condition.

Figure 3. InaGeoportal
Global forest change like its name has a mission to monitor forest change around the world. The data was derived from time series analysis of Landsat satellite imagery since year 2000 and continoulsy updated. When this article was posted, the most updated available data was for year 2014. Because it was derived from Landsat imagery, it has 30 metre resolution and can be used to do spatial analysis in medium scale (eg. 1:50000). Global Forest Change data is maintained by University of Maryland, Unites States. This data has global coverage and can be downloaded in tif format with a tile/scene size is 10 degree.

Global Forest Change Data
Figure 4. Global Forest Change Data
Soil Grid provides soil data in global scope. Because of its global coverage it has a coarse resolution and accuracy, compare to soil data at national or district level. The data was derived from statistical analysis of global soil data which include several properties such as soil classification, carbon content, pH, etc. The data can be downloaded in geotiff format.
Figure 5. Soil Grid Data