Del.icio.us lets you bookmark and tag any link you come across, and add your own description and notes to help you find it more easily later. You can share the information you've collected with others, and automatically see pages relating to the ones you've stored.
Furl stores full copies of any page (up to 5GB total) and allows you to search through the personal archive you've built up, as well as share material you've collected with others. You can subscribe to the furl lists of others via email and rss.
Simpy lets you store public and private bookmarks, add notes to each bookmark, and search the full text of the page behind each bookmark. The service periodically checks to see if any bookmarks have expired, and flags them for attention. Bookmarks can be imported from most major browsers, synced with del.icio.us, and exported.
Users can add their Adsense code to their stored Simpy information to earn from other people visiting their pages.
Spurl lets you tag and annotate pages you want to revisit. A copy of the page is saved so that you can view the content again even if the original site has changed. You can import your system bookmarks into Spurl, and the service interfaces with del.icio.us. The optional Spurl toolbar gives you greater control over your stored data.
Worth a look if you're willing to pay...