Here are some howtos to give you some sample uses.

Howto (expandable-content) - using php
Describes how to convert an script taken from another author to a moslate using php.

Howto (expandable-content2) - using logic
Same as above but uses logic instead.

Hello PHP World
Start to execute PHP in content items and create your own Moslate in the end.

Include external scripts
Describes many ways to let you include external scripts.

Link to other Content Item
How to link to another content item (there will be an easier solution built in Joomla).

Insert Google Map
Learn how to insert Google Map on your homepage.