Virtual Observatories and Star Maps

• Stellarium - the best free planetarium software you can download
• Skymap - Good for beginners
• The STScI Digitized Sky Survey Get an image of any astronomical object using the DSS retrieval form
• SkyView SkyView is a Virtual Observatory on the Net generating images of any part of the sky at wavelengths in all regimes from Radio to Gamma-Ray.
• SkyMap Interactive sky map using Sloan DSS
• Ciclope Astro - Planetarium on the web using WEB2.0 techniques.
• Free Astronomy Software - A nice list of all the packages ever made.
• Sky View Cafe - A Java-based planetarium website.

Weather Services and Satellite Imaging

• Clear Sky Clock
• Weather Underground
• SSEC Realtime Data Current satellite images
• Weather Net
• Weather.com The Weather Channel's home page

Cool groups and organizations

• San Francisco Amateur Astronomers (SFAA)
• International Dark-Sky Association
• Astronomical Society of the Pacific (ASP)
• San Francisco Sidewalk Astronomers
• Astronomical Association of Northern California (AANC)

Astrophotography & other How-to's

• Canon EOS
• Firmament Observatory - Lots of good info on how to use a telescope
• Astropix.com - Astrophotography
• Pete's Astrophotography - Classic Astrophotography

Abstract Services

• NASA Astrophysics Data System
• Service of Abstracts at CDS
• European Space Information System

Astronomical Events & Publications

• Space Calendar
• Astronomy.com
• Sky and Telescope

Astronomical Data Bases and Images

• NASA Remote Sensing Data and Information
• Hubble Space Telescope Public Pictures

Reference

• Handbook of Space Astronomy & Astrophysics

General Overview and Cool stuff

• The Nine Planets
• JPL's The Basics of Spaceflight
• SETI