I regularly save links to web apps, utilities and services that I think might be useful or interesting to my Diigo library. Diigo is a free-to-use service that lets you save, tag, annotate and share bookmarks using a browser toolbar or bookmarklet.
I’ve been using it for some years now and it’s grown into a decent research tool and now lets you save web pages for reading later, highlight and annotate web pages, build lists and more. There’s also a social element in that you can join groups and follow other users. There are even some premium features if you want to pay them some money but the basic service is totally free.