Georgopoulos P. (2008). A multiscale approach for assessing the interactions of environmental and biological systems in a holistic health risk assessment framework. Water, Air, and Soil Pollution: Focus 8(1): 3-21. DOI:10.1007/s11267-007-9137-7 [DOI link]
http://dx.doi.org/10.1007/s11267-007-9137-7
http://www.springerlink.com/content/5r8100723p704h16/fulltext.pdf

here’s some things that NEIC uses that might be of interest:

Pacific Northwest National Laboratory Infrared Spectral Library
IRIS database (toxicological information)
NIST CHEMBOOK
Envirofacts (TRI)
RCRA Online (policy letters)
SW846 online (hazardous waste methods)
OW methods databases
Henrys Law constant database

They also use EPA Models such as Minteqa2, Screen3, ISC, Water9, IWAIR, and AERMOD, but these may not fit within the database framework of the Data Finder site.

Examples – Daily frequency of comments, where are comments comming from, how many new datasets suggested, how many suggestions incorporated / pending / turned down, how many bugs identified. Later we will also want to know, how many datasets downloaded? How many datasets accessed? By whom (generally) ? We have the technology. How will measure sucess or failure?

Hazardous Waste – link to RCRAInfo rather than (or in addition to) the RCRAOnline document database. Your definition of data stresses websites where numerical data can be downloaded. I would think RCRAInfo would be the better link for DataFinder to highlight.
http://www.epa.gov/enviro/html/rcris/rcris_query_java.html

I searched for PCBs and no results were found. What about linking to http://www.epa.gov/epawaste/hazard/tsd/pcbs/pubs/data.htm?

For the Climate Change topic, you might want to include a link to this page on Renewable Energy.
http://www.epa.gov/renewableenergyland/
The data is stored in an Excel file and posted as a Google Earth file also.

CHAD, of which I am the developer, is a database of human activities, and as such best fits in:  Health Risks / Exposure.  It has almost nothing about Health Effects in it, but is used to do exposure assessments.  It should be located where HEDS is, developed also by our Division in NERL.  By the way, it soon will be part of HEDS, which will be used as a portal.

DESCRIPTION: ACToR (Aggregated Computational Toxicology Resource) is a collection of databases collated or developed by the US EPA National Center for Computational Toxicology (NCCT). More than 200 sources of publicly available data on environmental chemicals have been brought together and made searchable by chemical name and other identifiers, and by chemical structure. Data includes chemical structure, physico-chemical values, in vitro assay data and in vivo toxicology data. Chemicals include, but are not limited to, high and medium production volume industrial chemicals, pesticides (active and inert ingredients), and potential ground and drinking water contaminants.

URL: http://actor.epa.gov/actor/faces/ACToRHome.jsp

ORGANIZATION: ord

GEOGRAPHIC_SCALE: National

REGISTRY_SYSTEM: No

REGISTRATION: No

SERVICE: None

DESCRIPTION:

URL:

ORGANIZATION: Region 5′s Office of Regional Counsel

GEOGRAPHIC_SCALE: Regional

REGISTRY_SYSTEM: No

REGISTRATION: No

SERVICE: None

COMMENT: I would like to see this tool be used to retrieve environmental enforcement data (e.g. injunctive relief, penalties, supplemental environmental projects)