Sky Maps and Planetaria
Provides detailed and high quality sky maps, free for personal use and highly recommended.
http://www.skymaps.com

Starry Skies
Charts for the 88 constellations and their mythology. Details about the more prominent stars in each constellation.
http://www.starryskies.com/sitemap.html

Stellarium
Free software which renders realistic skies in real time. A super little planetarium program. Free download. The constellation art is very impressive. Shows planets & nebulae. You also get an interesting day time view.
http://stellarium.free.fr/

Moon - Interactive Atlas
An excellent resource for those interested in observing the moon.
http://www.lunarrepublic.com/atlas/index.shtml

Virtual Atlas of The Moon
This free software can visualize the Moon aspect for every date and hour. There is an excellent search facility and you can zoom in and track down most lunar features. Useful descriptions and supporting data are also provided.
http://www.astrosurf.com/avl/UK_index.html

Solar Eclipses - Past and Future
Search back through time and into the future, from different locations on Earth.There are excellent animations on the HM Nautical Almanac Office website.

Observational Astronomy
This is an excellent site. This Website contains images and resources about observering skills that are used in amateur observational astronomy. Members who are not active observers will also find lots to interest themselves here.
http://www.stargazing.net/david/

Albert L. Ruppel Observatory
Gregg's Astronomy Page - do not be put off by the title. This is the website of the Albert L. Ruppel Observatory, it hosts some superb images.
http://www.ruppel.darkhorizons.org/

Observing With Binoculars
Guides to constellations in different seasons and also to the northern and southern circumpolar sky.
http://www.dibonsmith.com/binoc.htm

Heavens Above
A resource dedicated to tracking satellites, flares for Iridium satellites, the International Space Station and many other objects.
http://www.heavens-above.com

Night Sky Observer
Lots of useful information including details of Jupiter's moons. Lots more.
http://www.nightskyobserver.com/skynotes.htm

Solar Eclipses - Safe Viewing
For advice on safe viewing, there are lots of ideas on the Eclipse Chasers website.

Explore The Universe
If you looking for a direction to your observing this is for you. Thanks to the Royal Astronomical Society of Canada's Observing Committee. Here is an observation schedule of planets, the moon and the constellations.
http://cobalt.golden.net/~kwastro/star101/pdf/ExploretheUniverse.pdf

Stars
Regularly updated. Excellent resource for details about stars and constellations. Photographs and lots of accessible theoretical information about stars.
http://www.astro.uiuc.edu/projects/sow/sowlist.html

Messier Objects
An excellent source of information.
http://www.ast.cam.ac.uk/~ipswich/Observations/Messier_Obs_Proj/Messiers.htm

Messier Objects - Non-Stellar Objects
The Your Sky catalogue is an excellent source of information.
http://www.fourmilab.ch/yoursky/catalogues/messier.html

Deep Sky Database - an online observing list generator.
This site is an online observing list generator for amateur astronomers who love to pursue deep sky objects; consisting of over 10,000 records.
http://www.virtualcolony.com/sac/

Observing Messier Object With Binocculars
There is lots of good advice and ideas on the Astronomical League site.
http://www.astroleague.org/al/obsclubs/binomess/binomess.html

Webcam Astro Images
A really good site with lots of advice and images.
http://www.astrosurf.com/re/qc.html

K3CCD Tools Homepage
Downloads and extensive photo gallery.
http://www.pk3.org/Astro/index.htm?k3ccdtools.htm

An Idiot's Guide to K3CCD Tools
How to get your first images - quick and easy. Manual processing when using an unguided telescope to capture lunar images. Straight forward instructions.
http://www.westcornwallastrosoc.org/idiots_guide_K3CCD_tools.php

Registax
Free imaging software.
http://registax.astronomy.net/

Astronomiser
A commercial site offering webcam modifications to allow for long exposure astrophotography.
http://astronomiser.co.uk/toucam.htm

Contemporary Laboratory Experiences in Astronomy (CLEA)
Here you will find an excellent set of laboratory simulations from measuring the height of lunar craters through to photoelectric photometry of the Pleiades.
http://www.gettysburg.edu/academics/physics/clea/CLEAhome.html

Astronomy On-Line Learning Centre
Animations and an extensive set of interactives to boost and clarify your understanding. Well worth a visit.
http://highered.mcgraw-hill.com/sites/0072482621/student_view0/interactives.htmlh

British Astronomical Association
The voice of amateur astronomy in the UK.
http://www.britastro.org/main/observe.html

Astronomy Now On-Line
Latest news across the whole of astronomy.
http://www.astronomynow.com/

Regulus Newsletter
A really useful astronomical resource from the Northwood Ridge Observatory, New Hampshire.
http://www.regulusastro.com/regulus.html

Sky and Telescope
The website of the magazine featuring lots of breaking news and advice for experienced as well as those new to astronomy. It also includes an interactive star chart.
http://www.skyandtelescope.com

Scientific American Magazine
Current developments and debate across the field of science. There is always something of interest of an astronomical nature.
http://www.sciam.com

Astronomy for Beginners
This is a excellent site for both those new to astronomy and for more experienced members. Many useful links.
http://www.astronomyforbeginners.com

Backyard Astronomer
Useful for beginners and of interest for more experienced members. Lots of useful ideas and advice with a focus on observing.
http://www.backyard-astro.com

NightSkyInfo.com
Run by amateur astronomer Emil Neata. An interesting site to browse through. Lots of basic information, finder charts, 'The Sky This Week' and links to various astronomy suppliers. Well worth a look!
http://www.nightskyinfo.com

The Sky
A really useful site for beginners. Lots of basic information. Guides, advice, calendars, games and lots more.
http://www.seasky.org/sky.html

Cosmology:The Study of the Universe.
This is a section from the WMAP website. It is a really good site for those wanting a short, concise but accessible introduction to cosmology.
http://map.gsfc.nasa.gov/m_uni.html

Introduction to Particle Physics
In the early history of the universe before the epoch of recombination, matter would not have existed. If you want to read up on particle physics the York University website is a good starting point. The material presented here is very accessible and well organised.
http://blueflag.phys.yorku.ca/yhep/ppp.html