A service that logs into XMPP servers and tests their compliance with various XEPs. Generates a visual map of compliance on a categorical grid. You have to give it a user account on the server so it can log in and run tests. You do /not/ have to add your server to the public roster!
There is also a command line tool in Github.
The first of several wiki pages at elinux.org which comprise a hardware compatibility list for the Raspberry Pi. You might want to have this page loaded on your phone or tablet when you go shopping for new peripherals.
FrequencyCheck is a website that helps you determine if your current cellphone will work on the cellular networks of a particular country. You can either search for devices compatible with a particular carrier, or carriers compatible with a certain mobile device.
3747 links, including 200 private