Challenging Observing Projects for Amateur Astronomers
Deep-sky site challenges amateur astronomical observers.
http://www.angelfire.com/id/jsredshift/

Drawings of Deep-Sky Objects with Large Telescopes
Site also has a link to discussions on visual observing.
http://members.fortunecity.com/faintfuzzy/

Observing Supernovae
Site has an in-depth FAQ on how to observe faint supernovae, and what you need to do so. Site also links to references for confirming your observations.
http://www.chapman.edu/oca/benet/observe.htm

List of Common Deep-Sky Catalogs
Listing of various common catalogs of deep-sky objects, along with abbrevations and short descriptions.
http://www.seds.org/messier/xtra/supp/cats.html

Radek's Observing Target List (ROTL)
Project to develop comprehensive set of finder charts for deep-sky objects. Includes basic data for and charts to locate objects with your telescope.
http://littlenet.com/astro/index.html

Iiro's DeepSky Pages
Video clips, pictures, sketches, and reports.
http://deepsky.iwarp.com

Planetary Nebulae Observer's Web Site
Planetary nebula data, images and information on over 1000 planetaries.
http://blackskies.com/

NGC/IC Project
Objective is to correctly identify all of the original NGC and IC objects. Starts with the original discoverer's notes and moves forward to encompass the work of contemporary astronomers, both professional and amateur.
http://www.ngcic.org/

The Messier Catalog
Images and information for all Messier objects from Students for the Exploration and Development of Space (SEDS).
http://www.seds.org/messier/

Ian's Astro Page
STCs.
http://www.nabu.net/astro/

Impressions of the Deep Sky
Links to deep sky sites, sketches and photographs.
http://www.skyrover.net/ds/

Messier45.com
Online tools for deep-sky observers, including maps and lists of objects with pictures and data.
http://Messier45.com/

Deep-Sky Collections and Catalogs
Links to deep-sky catalogs and observing lists.
http://seds.lpl.arizona.edu/messier/xtra/similar/catalogs.html

Deep Sky Observer
Information, images, charts for the Messier, Caldwell, NGC, and Hubble with search tool.
http://www.utahskies.org/deepsky/

The Caldwell Objects
Information, images, charts for the Caldwell Objects as taken from the weekly Utah Skies Report
http://www.utahskies.org/deepsky/caldwell/index.html

Messier Marathon
Includes instructions, complete biography, annotated catalogue and search tool.
http://www.messiermarathon.com

A CCD Tour of the Universe
Includes deep sky objects search, images of all Messier and many NGC and IC objects, mosaics of large nebulae and galaxy clusters.
http://astrosurf.com/jwisn/

Deep-Sky.Org
Features a reference of Messier objects, telescope information, and deep-sky links.
http://deepskyorg.tripod.com/

Ray Cash's Deep-Sky Page
Photos and information about deep-sky observing.
http://members.aol.com/anonglxy/deepsky.htm

Arp's Catalog Of Peculiar Galaxies
Summarizes catalog of 338 peculiar galaxy views gathered by Dr. Halton C. Arp in his Atlas of Peculiar Galaxies.
http://members.aol.com/arpgalaxy/index.html

Deep-Sky.Org
Features a reference of Messier objects, telescope information, and deep-sky links.
http://www.deep-sky.org/