The plugin works in component, modules and contacts in Joomla 3.x, 2.5 and 1.5 without hacking Joomla!

For modules you can use custom html module and place {mosmap} in the text of the custom html module. make sure the module is shown on the website. Don't make the map too big because modules normally don't have much space on an website. Use a lightbox so the visitor can make the map bigger on the page.
You can set the option prepare content to yes so the plugin will run (not required).

My example on the homepage has the following code:
{mosmap width='150px'|height='150px'|showMaptype='0'|Overview='0'|zoomType='None'|lightbox='1'|effect='vertical'}

For contacts, make a contact and in the field Other Information place the code for {mosmap}. Make sure the contact is reachable on the site.

For component place the {mosmap} code in an available field.
Other option is to hack or override a template of the component and add:
{mosmap lat='x'|lon='y'}
or
echo "{mosmap lat='".$field->x."'|lon='".$field->y."'}";