Here are a bunch of useful resources from around the net. If you have your own link collection that may be useful. If you know of a site or tool that may be useful, just add it below. I'll add it to the main list.
A fantastic reference for artists. Features everything from clothing, anatomy, vehicles, architecture and much much more.
Sublink: Anatomy reference at the Art Morgue
Conceptart.org the premier website for concept artists has a huge reference guide via it’s forums. This member contributed resource is massive and awesome. Covers anatomy, vehicles, character design and much more.
Human Anatomy Reference
Another great reference, though much of it is paid, commercial content. Still, if you don’t got the honey, there’s still the free samples pages you can mooch off of.
A resource primarily for human anatomy reference. Don’t miss the Andrew Loomis anatomy books.
A huge collection of human body reference shots. A lot of it is nude photography so if you’re in a public space put on a beret.
An unrealistic, but useful animation of a skeleton running. Useful to understand the structure of the human skeleton. The link leads directly to the mpeg file.
The Fantasy Art resource project at Elfwood has this useful hand reference guide. Loads of pictures of hands from various views. Especially useful because the hand is one of the toughest to draw from memory.
Katherine’s blog teaches life dfrawing sketches. A very useful resource, especially in learning to model the human body through speed sketching.
You could be forgiven for thinking this is a soft-porn site. Domai has been collecting pictures of beautiful women for years, and all of them with not a stitch of clothing to share. A great resource for learning to draw the female nude.
I originally found Domai on this conceptart.org thread which has some other great resources too.
Not really a skeleton in the real sense, but provides a wireframe with points of reference. May be useful for practice.
Other Useful Reference
This is a resource dedicated to character designers. If you enjoy creating the un-dead, gargoyles, seadragons, orcs or politicians, then you need to see this site.
A reference resource of flowers, plants, gardens and the creatures that inhabit them. A really nice resource for those that study nature.
A beautiful compilation of tree drawing information over at Squidoo.s A visual treat.
Schliffkopf’s collection of nature sketches. His sketchbooks are fascinating and this is a hugely inspiring collection. A must for every sketch nut that loves studying nature.
An all round artist’s resource, Maurice teaches you everything you need to know to start painting. The tools, techniques and even skills such as composition, lighting and stylisation.
A useful resource section at Windsor and Newton that explains the properties and techniques of working with various media such as watercolours, oils, gouache and pastels.
Helsinki Looks – A photo archive of street fashion from the streets of Helsinki. Very interesting and useful resource.
Great Artist’s Reference
A massive reference resources to great artists and their work. Provides insightful and useful information to artist’s, their techniques and the personal and social contexts to their work.
John Singer Sargent.org features an amazing collection of Sargent’s works. Dedicated exclusively to this amazing man, it features a massive collection of his work.
A massive collection of the venerable english landscape artist. A fantastic resource for those who enjoy drawing from nature.
A fascinating guide to the inside of the artist’s head. Features some truly visionary artists.
Features the sketchbooks of 10 great artists including John Singer Sargent and Benjamin Champney