Wakelet: Add links, notes, images, tweets, videos, and files to a collection. Click the three-dots icon while viewing a collection to get embed code.

Edshelf: Teachers can put apps and websites into online collections. Edshelf provides a widget for each collection of resources. 

List.ly: Enter web links into a list and embed. Free accounts are limited to 10 items in a list.

TES Teach with Blendspace: Gather a set of resources and put them into a widget with Blendspace. Those resources can be any combination of web links, online videos, documents, and text. Each item is numbered and is automatically given a thumbnail preview image. You will need to copy a public lesson to your account before you can share as an embedded widget.