Beyond the Messier List
Seen all the Messiers? Getting tired of showing the same ol' "showpiece objects" at star parties? Has "aperture fever" struck, and you've acquired another, larger telescope... now finding yourself wanting to put it through some paces?
If you don't have Burnham's Celestial Handbook yet, you need to get it! The pictures alone will inspire any budding deep-sky observer to seek out these objects.
You will also need a good celestial map. When not generating my own maps from MegaStar (below), I use Uranometria.
Most people in the above predicament(s) "graduate" to the Herschel 400 list. Sir William Herschel was perhaps the greatest visual observer of all time; cataloging, along with his son John in the southern hemisphere, most of the New General Catalog of nearly 8,000 objects, about 200 years ago. His favorite telescope was 18" in diameter. The Astronomical League of Florida offer an observing certificate for observing their favorite 400 Herschel objects, as well as other observing certificates: check them out! Some renegade deep-sky observers, myself included, have an unnatural aversion to "certficate programs"; not to mention such mundane (forgive me!) objects as open star clusters--of which there are many in the Herschel list and catalog.
A better list of about 400 deep-sky objects, I think, is Steve Gottlieb's favorites which can be found plotted and listed (with a short description of each object) on Orion Telescope and Binocular Center's DeepMap 600 (110 of these objects are Messiers; another 100 or so are double, multiple, variable, or "colored" stars; which are, of course, deep-sky objects too).
Steve Coe's fine list of 393 NGC objects can be found on David Chandler's DeepSpace star-charting software. Steve also has extensive notes, arranged by constellation, on the Saguaro Astronomy Club's Website.
Two of my favorite lists come from the Royal Astronomical Society of Canada's Observer's Handbook, which is published annually (but you only need to buy it once for the following lists). Alan Dyer's "The Finest N.G.C. Objects" offers observers 110 excellent objects beyond the Messiers; they are sorted by season, and contain a short description of each object. "Deep-Sky Challenge Objects," also compiled by Alan Dyer as well as Alister Ling are what the name implies: challenging objects for apertures 10" and above. This small paperback has other lists as well: "Galaxies with Proper Names," a couple of "brightest and/or nearest" galaxy lists, a double star list, and a variable star list.
I do not recommend Patrick Moore's so called "Caldwell List." Besides being tremendously presumptuous for attempting to name well-known deep-sky objects after himself, there are objects included in his list that no amateur observer has ever seen! If this list was prepared from photographs of deep-sky objects (which is what many suspect), it should not be pawned off to visual observers! Shame on Sky and Telescope for promoting it!
Arp galaxies are a fun group of peculiar galaxies to look for. Dennis Webb has a very fine WebPage devoted to observing these.
With the plethora of excellent planetarium and sky-charting software available today, it is a simple task to "filter and sort" by type, magnitude, size, field of view, and location: This is what I use MegaStar for; as well as printing excellent finder charts.
RealSky, a digitally compressed (by a factor of 100) version of the Palomar Sky Survey on CD's, can be ordered through The Astronomical Society of the Pacific--most images on this site, for example, were generated with RealSky. One can, however, download superior images from the Palomar Sky Survey (only compressed by a factor of 10) at the Digitized Sky Survey (DSS) site.
Of course, don't forget the Web: check my Deep-Sky Links page for lists fellow amateurs have compiled.