NIST Digital Library of Mathematical Functions Presents the same technical information, in extended form as "Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables" edited by Milton Abramowitz and Irene A. Stegun. The DLMF may well serve as a model for the effective presentation of highly mathematical reference material on the Web.
NIST Chemistry WebBook provides users with easy access to chemical and physical property data for chemical species through the internet. The data provided in the site are from collections maintained by the NIST Standard Reference Data Program and outside contributors. Data in the WebBook system are organized by chemical species. The WebBook system allows users to search for chemical species by various means. Once the desired species has been identified, the system will display data for the species.
Wolfram|Alpha is an online service that answers factual queries directly by computing the answer from externally sourced curated data, rather than providing a list of documents or web pages that might contain the answer as a search engine.