What are some alternatives?
When comparing PostDiva and Diigo, you can also consider the following products
Lasso Content Curation - Become an information ninja. Stop losing the info you need.
Pocket - When you find something you want to view later, put it in Pocket.
elink - Create Beautiful Curated Newsletters & Web Pages in Minutes.
Raindrop.io - All your articles, photos, video & content from web & apps in one place.
DrumUp - Content Marketing & Social Media Management Software
Pinboard - Pinboard is a personal archive for things you find online and don't want to forget.