ECA&D: European Climate Assessment and Dataset. Daily data over Europe.
HadEX - global climate extremes indices. Comprises of 27 indices of temperature and precipitation on a 2.5° x 3.75° grid from 1951 to 2003. ( closely linked to ETCCDI, see above)
PCMDI: Program for Climate Model Diagnosis and Intercomparison. Hosting detailed versions of the IPCC scenarios and model runs. Also detailed descriptions about data available from IPCC and about all the GCMs.
ECMWF: European Centre for Medium-Range Weather Forecasts.
World Climate Data and Maps. German Weather Service (DWD). For example: gridded (0.5, 1, 2.5°) 50-year monthly precipitation climatology 1951-2000 for global land areas.
NCDC: National Climate Data Center. Amongst others: GHCN (Global Historical Climatological Network) data. Daily and monthly observational data worldwide.
hadobs.org - Met Office Hadley Centre observations datasets.
European Soil Portal Data and Maps about soiltypes, soil degradation, pH etc. Top source to start with.
GoGeo!. The place to discover geospatial information and services for those in education and research. Links to UK and international data and portals. Useful!