AstroEngine
Space science blog by Dr Ian O'Neill discussing astrophysics concepts in an informed yet informal way.
http://www.astroengine.com/
Astrophysics
E-Print archive since April of 1992.
http://www.arxiv.org/archive/astro-ph
Astrophysics
A short introduction to astrophysics with associated articles on a number of topics.
http://www.physicsplanet.com/articles/astrophysics
Astrophysics
Wikipedia article on this branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects and the interstellar medium, as well as their interactions.
http://en.wikipedia.org/wiki/Astrophysics
Astrophysics and Astronomy
Introductory essays on astrophysics and astronomy.
http://www.hpwt.de/Astroe.htm
Cambridge Relativity
Beginner's guide to all the basic concepts of Astrophysics written by active scientists at Cambridge University, UK.
http://www.damtp.cam.ac.uk/user/gr/public/
Canadian Institute for Theoretical Astrophysics
Nationally supported research centre. Find out about current research, upcoming seminars and job opportunities.
http://www.cita.utoronto.ca/
Dyson Sphere
A list of frequently asked questions with answers.
http://www.aleph.se/Nada/dysonFAQ.html
Encyclopedia of Astronomy and Astrophysics
Comprehensive archive of explanatory articles on all key Astrophysics topics, categorised and fully searchable; actively updated by the Institute of Physics.
http://eaa.crcpress.com/
Encyclopedia of Astrophysics
A free peer-reviewed online publication written by scholars from around the world.
http://www.scholarpedia.org/article/Encyclopedia_of_astrophysics
Fermilab Center for Particle Astrophysics
Partially funded by a NASA Astrophysics Theory grant, find information about the group's past and future meetings.
http://astro.fnal.gov/
Gravity is Cool, or, Why our Universe is Hospitable to Life
Text of the 1999 Oppenheimer lecture at UC Berkeley given by professor Freeman Dyson on the origin of life and other subjects.
http://www.hartford-hwp.com/archives/20/035.html
High Energy Astrophysics Group
Astronomical Institute, Ondrejov. Focuses on the research of cosmic objects in X-ray and gamma spectra region. General information, projects and workshops.
http://altamira.asu.cas.cz/
Living Reviews in Solar Physics
A peer-refereed, solely online journal publishing invited reviews covering all areas of solar and heliospheric physics research. Published by the Max Planck Institute for Aeronomy, Katlenburg-Lindau, Germany.
http://solarphysics.livingreviews.org/
NASA Astrophysics Data System
Search system for abstracts in astrophysics, planetary sciences and solar physics.
http://adsabs.harvard.edu/
Network Generator
Generates astrophysical reaction rates online using an extended database.
http://www-astro.ulb.ac.be/Netgen/form.html
Olber's Paradox
A well know problem from astrophysics, Olber's paradox (Why is the night sky dark?), solved. As well as Newton's related Gravity paradox.
http://www.ronaldkoster.net/olber.html
Physics Topics - Teaching Notes
Teaching notes on celestial mechanics, classical mechanics, and stellar atmospheres.
http://orca.phys.uvic.ca/~tatum/
Space Physics Textbook
A free online introduction to space physics in the areas of plasma physics, regions, phenomena, instrumentation and modeling. Last updated October 7, 2008.
https://wiki.oulu.fi/display/SpaceWiki/Plasma+physics
Temporal Annex
Information mostly on the fourth dimension and theoretical physics.
http://temporal_science.tripod.com/
The Astrophysics Spectator
Articles published on this site cover current research in astronomy and astrophysics, describe our current understanding of astronomical phenomena, and comment on issues related to astronomical research.
http://www.astrophysicsspectator.com/
The Electric Universe
Physics knows four forces; 20th-century scientists were convinced that one of those, the electric force, played no macroscopic role in the Universe; site explains why that is incorrect.
http://www.the-electric-universe.info/
The NASA Astrophysics Data System
The Astrophysics Data System (ADS) is a NASA-funded project which maintains four bibliographic databases containing more than 4.0 million records: Astronomy and Astrophysics, Instrumentation, Physics and Geophysics, and preprints in Astronomy.
http://adswww.harvard.edu/
The Structure, Stability, and Dynamics of Self-Gravitating Systems
An interactive Astrophysics textbook from Louisiana State University.
http://www.phys.lsu.edu/astro/H_Book.current/H_Book.html
Tuneable Heterodyne Infrared Spectrometer - THIS
Instrument pages for the transportable receiver designed for atmospheric and astrophysical observations in the mid infrared spectral region (7-28 m). Developed by the University of Cologne.
http://www.ph1.uni-koeln.de/node/304
University of Surrey - Department of Physics (Research)
University of Surrey abridged version of the book "Astrophysics" , with many links to relevant material on astronomy, astrophysics and cosmology.
http://www.ph.surrey.ac.uk/astrophysics/index.html