After you have finished key-framing your animation in blender, you are ready to render out your animation as a finished piece. "Rendering" means that blender will look at the light-source, object materials, textures and motions to produce an image or movie that reflects all these things. It is normal for blender to take hours to render out an animation, so it would be wise to render it on a personal computer over night.
Short rendering tutorial by Blendercookie.com
Here is a second tutorial with a quick tip on rendering animations:
The next stage (compositing) is optional and is only necessary if you want to add effects like changing the colour, saturation, or contrast of the overall render. Compositing in blender is similar to Photoshop as you can make many adjustments to the image after it has been captured.
Here is a tutorial on using the compositer to edit your renders.
The third step is to take multiple renderings of animations and merge them into one movie file and/or add sounds to the animation. You can do this all by using the video sequence editor within blender.
Here is a tutorial that shows you how to put individual renderings together and add sound if you want.
