Essentially, all you need is a lot of paper, a way to register your drawings, and a way to shoot/scan your drawings. There's also some animation software that can help you shoot your drawings and help compile them into an animation.
Animators usually use some kind of animation software that's hooked up to either a wecam or camcorder to quickly shoot their rough penciles compile them into a preview movie that allows you to quickly see what your animation looks like. That allows the animator to quickly see mistakes and where improvements can be made. Scanners are usually only used once the animation has been finessed and finalized, since the process of scanning your drawings is supremely slower than shooting them with a webcam/camcorder. Using a webcam or camcorder that is hooked up to your computer and pencil test software to capture frames, preview the animation quickly, and easily make changes is the quickest solution for line testing your animation.
If you want to use your digital camera, you need to find or build a support system so that it can be suspended pointing down at your paper. You also need a flat surface where you can lay your paper down underneath your camera. Ideally your flat surface where the paper is being laid down would be connected to the support that's connected to the arm. With everything connected, it stabilizes everything and eliminates unwanted movement. When shooting with a digital camera for animation, make sure it is completely on manual settings. No autofocus, no auto-exposure, no white-balance, etc. If your camera makes tiny auto-adjustments from picture to picture, your animation will have weird flickering effects throughout the video.
If you need to see what a pencil test station looks like, I can send you pics of the one I built.
Your paper also needs to be registered. Traditionally, a peg bar is used with appropriately hole punched paper.
http://www.lightfootltd.com/images/New-pegbar-chart-4b.gif
The peg bar with the rectangular slit - round hole - rectangular slit configuration is called an ACME pegbar and is considered to be the industry standard. However, since it can be hard to find a ACME hole puncher and buying pre-punched paper can get expensive, many independent and amateur animators use other methods to register their paper. Any system you can think of for keeping your papers in the exact same position while drawing or taking pictures should be fine. If you need ideas on how to do so, let me know.
To do the actual drawings, animators usually work on a light box, which is essentially just a box with a light in it. Cheap ones 10" X 12" ones can be bought from art supply stores. You can also try to build your own. But you don't really need a light box to animate. Any glass or transparent or semi-transparent plastic over a light source can be used to help you animate. Even that's not necessary. I carry around a clip board (ripped the clip part off) with a pegbar taped onto it so I can animate when I'm at school in non-animation classes, at cafés, or on long bus rides. I just flip pages constantly to not lose track of volumes, arcs, timing and pacing.
To pencil test your animation (and digitally ink or clean up your drawings) you're going to need some animation and/or digital image editing software. Don't use windows movie Maker or Adobe Premiere to actually shoot or compile your animation together. An animation program will make it easier to arrange, re-arrange, add and delete single frames. Typically, playing around with multiple single frames is kind of difficult and bothersome in video editors since they weren't designed with frame by frame animation as a primary function in mind.
Some of the better commercial 2D animation programs such as Digicel Flipbook, Toon Boom, TVPaint, TAB, and PAP, have Student or Express versions that are fairly inexpensive. However, you might be disappointed by how crippled these stripped down programs are compared to their more expensive Pro versions. But if you look hard enough you should be able to find them cracked online (rapidshare, bittorrent). There are some free alternatives.
To pencil test, I'd suggest MonkeyJam. It's free.
http://www.giantscreamingrobotmonkeys.com/monkeyjam
If you're on a Mac, use Pencil(there's PC and Linux versions as well).
http://www.les-stooges.org/pascal/pencil/index.php
Here are some online resources about the basic principles of animation. Reading and understanding these will teach you how to get the kind of movement you want in your animation, and make it easier to spot errors or figure out why your animation doesn't look quite like you had expected/hoped it would.
http://www.idleworm.com/how/index.shtml
http://www.awn.com/tooninstitute/lessonplan/lesson.htm
http://www.animationarchive.org/2006/05/media-preston-blairs-animation-first.html
http://www.animationarchive.org/2006/05/media-preston-blairs-animation-1st.html
http://www.karmatoons.com/drawing/1a.htm
http://www.animationarena.com/principles-of-animation.html
http://w ww.animationmeat.com/notes/notes.html