This will be an ongoing post:
Animation Career Pro: An all around great website, lots of tips and goodies!!
Creative Crash: this one is great. It has a lot of goodies. There are MEL scripts, Max scripts, characters, tutorials and it's mostly free, you have to register to download content, but it's worth it.
FOR GATHERING ANIMATION REFERENCEBBC Motion Gallery: By far the best website for gathering video reference. It has pretty much everything that you can imagine, humans, insect or animals
Reference! Reference: another great site for gathering video reference and facial expressions. Free database for animation.
Endless Reference: Want to created realistic reference that will blow your competition out of the water? Here, you can polish your skills and start producing world class animation in just 3 simple steps. Download, analyze and apply. Apparently you have to pay for a subscription... looks like a great site if you have some money.
YouTube: Another great site for getting video reference.
Movie Clips: Great for finding video reference based on what mood or a particular situation you're looking for. With over 12,000 movies clips, a good source of video reference and a great site for studying acting, timing and secondary characters.
Turbosquid: I'm sure most of you know about Turbosquid. It's a great site for downloading models. You can usually find a decent free one, but if you want a super rad detailed model it's going to cost you.
Jason Ryan Animation: Webinars: a great site with videos to download, also you can pay to subscribe to his past and present (and future) webinars. Jason Ryan is an animator that has great cartoony timing and style.
Sam 3D: the best part about Sam3D is that it acts a hub for a lot of different 3D sites. I usually go here before Turbosquid because it will check a variety of different sites then give you the option to pick where you're going next to find what it is that you're looking for.
http://www.moviewavs.com/ This is a great website if you're looking for some dialogue pieces to animate to without the hassle of watching your entire DVD collection, and ripping audio. It has a ton of great movies, cartoons, and TV shows with all different durations.
Animation Buffet: Lots of resources, characters, MEL scripts and tutorials. It's from Jean Denis-Haas who is a brilliant animator at ILM.
Animation Meat: This website is great for an overall "let's geek out on animation" type site. It's a great time killer with tons of filler. It has great insights into the animation industry and a lot of resources to absorb.
Pencil Test Depot: An amazing site that showcases old 2D Disney movie pencil tests, not to mention other awesome pencil tests... Tons and tons of animation goodness.
11 Second Club: This has tons of information, forum threads and resources available. It too is a monthly animation contest, they give you the audio file and you animate to it. You then turn it in and members vote. It's a great website to get some feedback or give some feedback and see what other animators are doing.
Gorilla Animators: Animation Resource Centre, lots and lots of animation goodness here!!
Free Textures: Get your free texture on!!
More Free Textures: More textures to boot.