What are some alternatives?
When comparing Pearltrees and Diigo, you can also consider the following products
Raindrop.io - All your articles, photos, video & content from web & apps in one place.
Pocket - When you find something you want to view later, put it in Pocket.
Tagpacker - A free tool to quickly collect, organize, and share your favorite links.
Pinboard - Pinboard is a personal archive for things you find online and don't want to forget.
Pinterest - Pinterest is a visual discovery tool that you can use to find ideas for all your projects and interests.
Google Bookmarks - With Google Bookmarks, you can save shortcuts to your favorite webpages and navigate to them in seconds from anywhere.