The Automatic Packet Reporting Service (APRS) is probably the most common use for packet radio today. While many believe APRS is just for tracking resources, there are lots of other uses for it which makes it a valuable addition to your ham radio tool box.
Get a Weather Report
WXBOT - Simply sending a message to WXBOT will give a basic weather report for your current reported location. However, you can get more detailed weather information by specifying where, when, or what. WXBOT allows for reports based on the location of a callsign, zip code, grid square, CWOP, or City, ST. The service allows for reports based on a certain day/night of the week. Also, a request can be made for either a brief or full forecast. For a full list of features, see the KI6WJP WXBOT Website
WXYO - Very similar to the above WXBOT, WXYO responds with brief weather forecast using the Open Weather API. More information is available at the APRS Romania Website.
Communication via Text Message
SMSGTE (Service Unavailable - Unfortunately this service is currently offline due to changes in regulations and apparent abuse by people sending spam messages.) - I find the SMSGTE service very useful. It allows users to send and receive text messages via APRS. To use the service, send a message to SMSGTE, then in the message line add @<number> <message>. Once a message is sent from a radio, they system can then forward replies back over RF. The service does have maintenance cost associated with it, so if you find it as useful as I do, please donate. You can get a full list of instructions and features at smsgte.org.
SMS - This is a newer service to send text messages to and from the APRS network. It is requested that users visit their website to opt-in to keep it working correctly. To utilize the service, send a message to SMS with the message @<number> <message> just as with the SMSGTE service above. For more information see the user guide at http://aprs.wiki/SMS/howto.html.
Send an Email
EMAIL - Being able to send email from APRS is a great feature. To use it, send a message to EMAIL with <email address> <message> in the message line. The full user manual can be found at aprs-is.net.
Lookup Callsign Information
WHO-IS - WHO-IS will allow a user to lookup a callsign using the QRZ.com website and retrieve information about the person behind the callsign. Full information is found at aprs-is.net.
APRSLink - APRSLink allows for access to the Winlink service from APRS. It can be used to read or send short email messages, get notifications when there are new messages, get information on the closest RMS packet station, or perform Winlink maintenance functions. The full manual is available at the Winlink site.
Spot Yourself during an Activation
APSPOT - This service lets you easily spot yourself during a SOTA, POTA, WWFF, or SiOTA activation. The service has quite a list of commands for sending the correct information based on what type of activation is being spotted, so I'm electing to simply point to the Usage Guide. For all the info, visit the APSPOT site at https://apspot.radio/.
Telemetry, Remote Control, and DIY
APRS gives you the ability to send all sorts of information back and forth over RF and the Internet. With telemetry, you can have a station automatically give you information from various sensors. A good example would be an APRS connected weather station. APRS gives you the ability to send/receive commands, such has turning a relay on/off remotely. These features opens the door on all sorts of DIY projects to apply APRS to.