Data.gov- Data.gov provides descriptions of the Federal datasets (metadata), information about how to access the datasets, and tools that leverage government datasets.
EPA data finder- This site is a single place to find a vast selection of EPA data sources, organized into topics such as air and water that are in easily downloadable formats.
ESA data registery The data sets registered here are associated with articles published in the journals of the Ecological Society of America. See individual registry entries for citation information as well as usage rights.
Ecological Data Wiki The site is as a source for identifying ecological datasets and quickly figuring out the best ways to use them. Just think of it as the Wikipedia of ecology data.
TreeBASE TreeBASE is a repository of phylogenetic information, specifically user-submitted phylogenetic trees and the data used to generate them. TreeBASE accepts all types of phylogenetic data (e.g., trees of species, trees of populations, trees of genes) representing all biotic taxa.
VertNet VertNet takes four classic vertebrate networks (FishNet, MaNIS, HerpNET, ORNIS), to combine them into a single integrated data portal.
DOE Data Explorer Use the DOE Data Explorer to find scientific research data - such as computer simulations, numeric data files, figures and plots, interactive maps, multimedia, and scientific images - generated in the course of DOE-sponsored research in various science disciplines.