If you are an animation lover and want to do get started with something very simple, then this animation application called Pencil is for you. With the advancements in the development tools, animation is now a fairly simple and standardized task. Visual effects, special effects and 3D graphics application are available from many vendors, but they require some serious skills and costs pretty high.
Pencil animation software
Pencil is a simple, plain and easy to use application with bunch of options under the hood. In fact I should be saying, it is very quick to get started with it any time even though, you may not have any experience with any drawings and effects software before.

Pencil animation tools
Pencil has many tools that can assist you making drawings and filling colors. They are:
Paint Brush
Polyline
Eraser
Modify Curve
Select Tool
Clear Button
Pen Tool
Color Picker
Paint Bucket
Move Tool
Zoom Canvas
Pencil animation features
Pencil, though a small application, has quite a few features that can come handy at times.
Layers
Drawing
Bitmap drawing
Vector drawing
Zoom and rotation
Animating
Adjusting keys
Importing images
Cameras
Sound
Under the Time Line tab it is possible to add layers such as a Bitmap Layer, Vector Layer, Sound Layer and Camera Layer. As its an animation application you can also add and remove KeyFrames.
Animation
Pencil allows you to create cartoons, animate images and add audio. Animation as usual, is done by adding multiple images or frames and then playing the sequence. The playing speed is set using the frame per second (fps) speed. A camera layer lets you define a particular view, with a certain aspect ratio, within your unlimited canvas. Whats more, you can define a view for each key of the camera track, and the view is linearly interpolated between the keys.
Pencil application is a portable application of size 5 MB and doesnt require installation. It has a well documented users manual that can teach all the basics and the advance features of the application. You can have a look at the user manual
here You can download the Pencil application
here.