With all the hubbub about the 150th anniversary of Origin, it's easy to forget that Darwin was more than just the father of modern evolutionary theory. He originally established his reputation with his geological research on the Beagle voyage. That was followed by the first extensive study of barnacles, published in four volumes (1851-1854). After that came Origin, which was followed by a book on orchid pollination. Darwin revised Origin five times and wrote related works on variation in domesticated animals and plants, the descent of man, and the expression of emotions in humans and animals. He produced other books, too, on such diverse topics as carnivorous plants and the action of worms.
I'm delighted to report that the works of Darwin have been reprinted once again by New York University Press. Previous hardback editions of this set of 29 volumes are priced at thousands, but this new paperback set goes for just $525. (Yes, CORE has a set on order.) Along with Darwin's published works, the set also includes Darwin's Beagle diary and what Francis Darwin called the Foundations of the Origin, transcriptions of Darwin's sketch of 1842 and essay of 1844. The Origin comes in both first and sixth editions. This is a terrific way to add the works of Darwin to any library.
If you can't afford the complete printed works of Darwin, you can still get access to all his written work through the Darwin Online database and the Darwin Correspondence Project. Darwin Online is an amazing website. Not only do they have his published writings (including everything in the series from NYU Press), but they've also amassed and transcribed Darwin's articles, manuscripts, notebooks, and works about Darwin. Most English versions of Darwin's works are present (including all six Origins), and numerous non-English books are also available. Voyage of the Beagle in Swedish? Got it. Origin in Polish? Got it. Insectivorous Plants in French? Got it.
In the manuscript database, Darwin Online has some very significant works. Both the original sketch of 1842 and the essay of 1844 (collected as Foundations of Origin in the NYU Press series) are available in PDF (if you feel like deciphering Darwin's handwriting for yourself). The original manuscript chapters of Natural Selection, the big book that Darwin abandoned in favor of the shorter Origin, are also present (3, 4, 5, 6, 7, 8, 9, 10). Users can also browse or search various notes and diaries made while aboard the Beagle.
In fact, there is so much material available at Darwin Online that wading through search results becomes daunting. It's actually helpful to know a bit about Darwin's life and work before trying to do a search. Otherwise, the volume of results to a nonspecific search like "creation" can be a bit overwhelming.
For even more Darwin writings, check out the Darwin Correspondence Project. The website is a companion to Cambridge University Press's Correspondence of Charles Darwin series, which just published its 17th volume (letters of 1869). The first fifteen volumes of the series are available in the database, covering Darwin's life up to 1867. There are 5000 letters transcribed in the online database, which is about a third of Darwin's total surviving correspondence. With Darwin's published and unpublished works at Darwin Online, the Correspondence Project is an invaluable tool for exploring the mind of Charles Darwin.
These online resources make Darwin studies easy even for an amateur like me. I found both sites indispensable when composing my response to The Darwin Conspiracy. With so much information readily and freely available, anyone should be able to accurately describe Darwin's arguments or opinions (provided, of course, they understand what they read). There really is no excuse for perpetuating conspiracy theories or old wives' tales.
On the other hand, if you're old fashioned like me, you still enjoy curling up on the couch or in bed with a good book, and websites just don't cut it. For us, there's always The Works from NYU Press to give us a gateway into the world of Charles Darwin. For Darwin research, however, the gold standard is online.