Have you been sharing links on Twitter and not saving them anywhere else? You soon realize that Twitter does not keep your history forever. So Packrati.us will automatically follow your Twitter feed and bookmark your shared links into your Delicious account (I prefer Diigo for bookmarks however).
You log in via oAuth, and they rely heavily on you merging your Yahoo and Delicious accounts as well. So make sure you have that in place. The FAQ covers it quite well on the site.
This is a great way to keep track. You could even establish an account on Delicious for just your Twitter feed to split shared links from your personal bookmarks. Any way you look at it, pretend it is a backup service for your shared links.