CalSky (sky calendar) was web based astronomical calculator used by astronomers to plan observing.The website, available in English and German, featured a calendar (and/or email notifications) generated for your location including information on aurora, comets, tides, solar and lunar eclipses, planets, bright satellite passes (ISS, HST, etc.), occultations, transits, iridium flares, and decaying satellites that may be visible.

The NASA Exoplanet Archive is an online astronomical exoplanet catalog and data service that collects and serves public data that support the search for and characterization of extra-solar planets (exoplanets) and their host stars.

The Extrasolar Planets Encyclopaedia[9] is an astronomy website, founded in Paris, France at the Meudon Observatory by Jean Schneider in February 1995which maintains a database of all the currently known and candidate extrasolar planets, with individual "note" pages for each planet and a full list interactive catalog spreadsheet. The main catalogue comprises databases of all of the currently confirmed extrasolar planets as well as a database of unconfirmed planet detections.

Galaxy Zoo is an online astronomy project which invites members of the public to assist in the morphological classification of large numbers of galaxies. It is an example of citizen science as it enlists the help of members of the public to help in scientific research. The current iteration of the project, launched in April 2010, is Galaxy Zoo: Hubble, and uses Hubble Space Telescope survey data. It is part of the Universe group of citizen science projects.

Telescopius is a web application with multiple tools, from a 15,000+ deep sky objects database and search, to a telescope simulator, astrophotography mosaic planner, and a social network for astrophotographers.