Twitter: Use Twitter's Widgets page to create a new widget. A widget can be a Twitter account's timeline, a single tweet, a list of liked tweets, a collection of tweets, a list of Twitter accounts, or Twitter search results. Three kinds of widgets are embedded below.

Pinterest: Use Pinterest's Widget Builder to embed a pin, board, or profile. Pinterest's widgets do require some extra code to be inserted near the end of your page. You'll see this mentioned in red on the Widget Builder page.

Periscope: Embed an on-air button that pulses red when a specific Periscope account is broadcasting live. When the button is clicked, a tab opens to the account's Periscope profile. See a bunch of these embedded buttons on my Educational Periscope Broadcasters page. To embed a replay of a Periscope broadcast, you'll need to embed the Twitter post with the broadcast link.