While there are many great resources out there to help you along your way to enjoying the hobby of astronomy, there's a few that I think you'll find very useful!
This is the International Occultation and Timing Association website. Their accurate information provided for viewers around the globe will prove invaluable.
This site is easy to use, concise, and offers perfect information and charts for viewing satellites, asteroids and often bright comets.
Space Weather will keep you up-to-date on solar and auroral events and well as many other things. This is definately a good tool!
The Astronomical League website offers many fine observing programs for the amateur astronomer and offers a wealth of resources including links to current information on comets.
"Your Sky" is a wonderful interactive planetarium tool that allows you to create customized maps and sky views specific to your location.
Sky and Telescope magazine offers terrific on-line tips, charts and information, as well as many articles for the amateur astronomer.
Astronomy magazine also has on-line resources, observing tips and more.
The Association of Lunar and Planetary Observers (ALPO) is a comprehensive, educational and very useful website.
The American Association of Variable Star Observers (AAVSO) will offer you the kind of information you need to study variable stars.
The Lunar Republic website offers up some of the very finest on-line reference materials available.
Although there are many, many more terrific websites out there, I think you'll find the ones listed here some of your most often used "tools"