• HNSky     Freeware for desktop/laptops.
• Stellarium     Freeware for desktop/laptops. Check Google Playstore/Apple Store for the mobile version.
  
• Skymaps.com     Free sky maps for Northern, Southern, and Equatorial regions.
• Sky Safari     Check Google Playstore/Apple Store for mobile version.

Satellite Resources

• Heavens-Above    Satellites and other astronomy information. Check Google Playstore/Apple Store for mobile version.

Light Pollution Maps

• Dark Sky Finder    Superposed "dark sky" color gradations on Google Map; Worldwide
• Light Pollution Map    Superposed "dark sky" color gradations on worldwide map.
• Check your Google Playstore/Apple Store for mobile versions of "Dark Sky Map" and/or "Light Pollution Map".
  

Solar and Lunar Observing and Eclipses

• Eclipse Predictions by Fred Espenak, Eclipse Wise. NASA/GSFC Emeritus    The resource for solar and lunar eclipses.
• Xavier Jubier's Solar and Lunar Eclipses
  
• MrEclipse    Resource for photographing eclipses.
• Solar Monitor
  

Weather

• Weather Spark
  

Video/Live Astronomy

• Night Skies Network     Where amateur astronomers broadcast views of the sky

Optics

• Telescope Optics Net    Informative site on telescope optics
  

Online Forums/Classifieds

• Cloudy Nights
• Astromart
• Stargazers Lounge

Equipment Manufacturers and Vendors

• Scope Stuff
• Astro-Physics
• Takahashi America, Europe, Japan
  
• William Optics
• Sky-Watcher
• Starlight Instruments (Feather Touch Focusers)
• Lacerta and its standalone autoguider
• Sky Rover
• Explore Scientific
• Tele Vue
  
• Taiwan, HK, Singapore Stores: Microtech, Sun Optical, Nick Enterprises, Cyclops Optics, Grand Eye Scientific Company,
  
• US Stores: BH Photo, Amazon, Ebay, Astronomics,
  
• UK Stores: 365Astronomy,
  
• EU Stores: Astroshop,