http://www.statistik.at/web_de/services/index.html
InfoChimps - all and everything, rather US-centred, mostly census-data:
http://www.infochimps.com/
BIOLFLOR - Comprehensive database on species traits of plant species (German flora), overwhelmingly extensive:
http://www.ufz.de/biolflor
GBIF - a compendium of almost all species-distribution databases available:
http://www.gbif.org/
IUCN-Webpage, spatial data for endangered species:
http://www.iucnredlist.org/
EEA, Eionet Central Data Repository. Spatial, environmental, diversity data, etc:
http://cdr.eionet.europa.eu/
i.e.: Invasive Species Reports:
http://www.eea.europa.eu/publications/streamlining-european-biodiversity-indicators-sebi
or CORINE Landcover:
http://www.eea.europa.eu/data-and-maps/data#c12=corine+land+cover+version+13
World Bank Data / Indicators:
http://data.worldbank.org/indicator
Climate Data:
http://climexp.knmi.nl/start.cgi?id=someone@somewhere
Soil Data:
http://eusoils.jrc.ec.europa.eu/library/esdac/OnLine_Data.cfm
File sharing & collaboration:
Github
Dropbox
Google Docs
buzzdata
i.e.: Invasive Species Reports:
http://www.eea.europa.eu/publications/streamlining-european-biodiversity-indicators-sebi
or CORINE Landcover:
http://www.eea.europa.eu/data-and-maps/data#c12=corine+land+cover+version+13
World Bank Data / Indicators:
http://data.worldbank.org/indicator
Climate Data:
http://climexp.knmi.nl/start.cgi?id=someone@somewhere
Soil Data:
http://eusoils.jrc.ec.europa.eu/library/esdac/OnLine_Data.cfm
File sharing & collaboration:
Github
Dropbox
Google Docs
buzzdata