|Applicable Blender version: 2.46.|
The output of the rendering process is generally a single image frame (which might be part of a sequence of images). However, instead of directly rendering all the elements of the scene into the output image, you may want to apply different effects to different parts.
To this end, it is possible to split out the elements of the rendering process (separate scene layers, also solid versus halo materials, Z-depth, sky background etc) into separate render layers which can then be fed into the compositor and tweaked in various ways to make up the final image.
Rendering by Parts (Bucket Rendering)
Images can be rendered in pieces or layers rather than all at one time. Your computer will only need to compute smaller bits of information thus using less memory. By changing the Xpart and Ypart values (up to 8 each since Blender can't support more than 64 [8x8] parts) in the Render panel of the Scene context(F10,) you can divide your image into an invisible grid. The pieces will layer one at a time until they are whole.
Edge Renderings - Tutorial Here
Blender has an option of adding a border – a defined edge to objects (like in cartoons). To do that you need to go to the render buttons (F10) and then, under "output" change the edge setting: set the "Eint" to a value of about 100 and check the "edge" icon to enable edge rendering. This would give you edge line at the edge of each polygon. To prevent it from applying on all polygons the same way change to "unified render" under the format tab. Then, in the edge settings change the "antishift" value, it will decrease itself from the fint value when the line is between identical materials. By also checking the "all" icon you tell the render to apply the edge rendering on transparent materials as well. In Blender 2.59 this seems to be integrated into the Render-properties in the subwindow 'Post Processing' as options 'Edge' and 'Threshold'.
Note: User Terrywallwork - The edge bordering feature in Blender 2.43 only seems to work when Blender Internal renderer is used, when Yafray is used, no edge is show even if the options is clicked. I'm not sure if there is a way round this or not.
HDRI Rendering - Tutorial Here
Multi Thread Rendering
Blender has the option to render with 'Multiple threads' meaning it can render more than 1 part at once. This is done by sending more than 1 Render parts to the CPU to process at the same time, if your CPU can handle it. The Option is found in render buttons (F10). Change the number of threads used by changing its number.
Note in Blender 2.46+: Blender 2.46 automatically selects the number of threads.