Sky Charting/Planning Tool Links
My favorite free planitarium software download.  A great planning tool.  Size and print your own star charts with as much or little detail as you need.  Excellent stuff.
An online interactive Sky Chart with nice features.  The star chart itself is so-so;  it's most usefull feature is showing a detailed representation of Jupiter and Saturn's moons at a given time.  You can even put it into motion by advancing the clock.

Cartes du Ciel
Similar to HNSKY, Cartes du Ciel is a download.  Create your own star charts with exactly what you want on them.

Virtual Moon Atlas
Just what it says, a Moon Atlas download of epic proportions.

Websites Useful for Planning an Observing Session

Saguro Astronomy Club Downloads
Great downloads.  They have Observation Logs, Lists of Doubles, Carbon Stars, Asterisms, Deep Sky Objects, and more.

Clear Dark Sky
An astronomers forecast chart for your location (or at least a nearby one).  Very useful chart depicting sky conditions, seeing, humidity, temperature, etc.  The chart itself is clickable and provides forcast maps for each detail.  1000's of locations in the U.S., Canada, and Mexico.

Unisys Weather Satellite Image
Great Satellite Weather depiction.  Select the geographical region, type of image, time, or loop animation.  Very user friendly.
A planning tool for observing Messier and Hershel objects, month by month.
The hottest Messier Stuff available online.
North Central Kansas Astronomical Society's list of carbon stars, by constellation.
A great Double Star Log/Listing
The top 200 Most Beautiful Double Stars, a nice listing.

Observatory and Spacecraft Images
The Hubble Space Telescope site.
The European Southern Observatory website.
What's up with our Sun and Solar System.  One of my daily visits.
The Goddard Space Flight Center's Solar Dynamics Observatory.

Astronomical Organizations
The Astronomical League website.  Many observing lists and clubs for specific types of objects, i.e., Messier objects, double stars, etc.
The Royal Astronomical Society of Canada website.  Many observing lists and programs, similar but different to the Astroleague above, and a lunar observing program as well.

Great Websites You May Like

Rather simply named, this website is the brainchild of Jim Kaler, Prof. Emeritus of Astronomy at the University of Illinois.  You can spend countless hours on this site.  If it has to do with stars and constellations, it's here.  A fabulous site about stars. 

Cloudy Nights Telescope Reviews
Reviews of all kinds of equipment, extensive classifieds with good deals on used equipment, great information.

The Nexstar Resource Site 
Celestron Nexstar Telescopes are very popular.  This site is great for owners of these scopes.  Much useful information and Nexstar specific downloads.
A website named "Earth and Cosmos".  A very attractive site from "down under" well worth checking out.  Nice astrophotos taken by Paul.