Databases for vegetation scientists

Plant traits:
BiolFlor - Search and information system on vascular plants in Germany
CLO-PLA - Database of clonal growth in plants
LEDA - Life-history traits of the Northwest European flora
USDA PLANTS Database - Provides standardized information about the vascular plants, mosses, liverworts, hornworts, and lichens of the U.S. and its territories
University of Connecticut Plant database - Dedicated to the ornamental attributes, appropriate use and identification of landscape plants

Plot data:
Global Index of Vegetation-Plot Databases (GIVD)
Austria: Austrian Vegetation Database
Czech Republic: Czech National Phytosociological Database
Denmark: DANVEG
France: EcoPlant | National Forest Inventory | SOPHY
Ireland: National Vegetation Database
Netherlands: National Vegetation Databank
New Zealand: National Vegetation Survey Databank
Slovakia: Central Database of Phytosociological Relevés
Spain: Biodiversity databank of Catalonia | SIVIM
UK: Countryside Survey | National Vegetation Classification
USA: LTER Data | USGS - NPS Vegetation Inventory Products | VegBank
Tropical Forests: Gentry Dataset | RAINFOR

Plot databases systems:
TurboVeg
VegAna (Vegetation edition and Analysis) is an integrated software package oriented toweards the storement, management and analysis of ecological data.
VegBank (online archive) & VegBranch (desktop)

Taxonomic & Floristic Data:
Atlas Florae Europeae
FloraWeb
Integrated Taxonomic Information System (ITIS)
International Plant Names Index
International Working Group on Taxonomic Databases
Mexican Biodiversity Information Network - REMIB
NatureServe Explorer - Community and Species classification
USDA Plants Database
VegBank -- ESA Vegetation Panel Plot Archive
W3 TROPICOS