Decrease size of a avi video with lowest quality loss
Now you've actually finished your question, the simple answer is to encode it using h.264/mp4. Blender can render to h.264, using ffmpeg video in the render settings but the better way is to render to image sequences and convert.
Since you have a render, you can convert it to h.264 / mp4 without having to re-render. There are many ways to do this, ffmpeg being one of the best, but if you prefer a GUI then Handbrake is a good option.