MapPress adds an interactive map to the wordpress editing screens. When editing a post or page just enter any addresses you’d like to map.

MapPress will automatically insert a great-looking interactive map into your blog. Your readers can get directions right in your blog and you can even create custom HTML for the map markers including pictures, links and etc…

Pricing: Free
Requirements: WordPress 2.5+
Source: http://wordpress.org/extend/plugins/mappress-google-maps-for-wordpress/