The SearchEngine3 module allows people to search your SpaceNode by typing in the keywords they are looking for.
If you have more than one SpaceNode then you can setup this module in a folder on your SpaceNode and configure it to return search results from all your SpaceNodes. You just need to type their domain names into the appropriate 'module settings' when editing the folder. The maximum limit of spacenodes that can be searched is 255 chars to enter all their domains separated by the comma char. eg: 'alexkent.com,djalexkent.com,spacenode.com'
Your SpaceNode is normally visited by the SpaceNodeSpider once per day, however pages that do not change very often might be visited less frequently. This is the reason why new articles recently added do not show up immediately and also why new SpaceNodes might not have been indexed at all yet.
You can also add a 'SearchEngine' block so that your users can be on any page and search your SpaceNode. If you setup your SearchEngine3 module on any other address than 'http://yoursite.com/search/' then you need to change the setting in the block.