Imagecache is a dynamic image manipulation and cache tool.
It allows you to create a namespace that corresponds to a set
of image manipulation actions. It generates a derivative image the
first time it is requested from a namespace until the namespace or
the entire imagecache is flushed.


Usage:
goto  Administer, select the "By Module" tab, and then click "Image cache"
in the "Imagecache" section.

Enter a name of your choice (e.g. 'scale200x200') into the "Preset namespace" box,
and click on "Create preset".

Select what you want to do: you have a choice of "scale" (which reduces an image
to the size you specify), "resize" (which may expand and crop your image to
fit a particular size), or "crop". Press "Update preset".

Now fill in the parameters for your action, and press "Update preset" again.

If you want, you can add a series of actions to the same preset (not quite sure 
why you would want to do this).

The preset can then be put into use in various other modules. For example, in
CCK, you can use the "Manage Fields" tab to choose presets to be applied
to CCK image fields when displaying them. The Inline module also allows you
to choose an Imagecache preset - but beware, Inline 5.x-1.1 does not
work with Imagecache v2, you must not upgrade beyond Imagecache 5.x-1.5. 

add a 
print theme('imagecache', $ruleset_namespace, $image['filepath'], $alt, $title, $attributes)
to your tpl.php file where you would like the image to appear, where $alt, $title and 
$attributes are optional parameters.