Searching for Content Based on Location with Search API Location
The Search API Location module adds support for indexing location values provided by the Geofield module and subsequently filtering or sorting on them, provided the service class supports this. Currently, only the Search API Solr module is known to support this feature.

Search API Location adds a new data type, "Latitude/longitude" to the list of fields in the Search API index. We can use this to index the Lat/Long Pair property of Geofield fields. First, we have to add the location field to the list of fields to index. In this video, I will show you how to do that, edit the Search View and add a filter criteria for location.

Using a Slider to Filter Search Results With a Numeric Field with Search API Ranges
Search API Ranges gives search facets the ability to add a slider widget for numeric fields. In this video, we will add a slider facet that will allow us to narrow our search based on the price field.

Searching the Content of Attached Files with Search API Attachments
The Search API Attachments module indexes the content of attached files (.txt, .pdf, etc.) using Solr. In this video, I will show you how to configure the Search API Attachment module to do that.

Saving Searches to be Notified of New Content
The Search API Saved Searches modules gives you the ability to save searches executed by Search API and be notified of new results via email.