I'm a big fan of del.icio.us. In fact, I've come to rely on del.icio.us because of how easy it is to organize and access my links. But I also like the convenience of having bookmarks in my browser. I realized yesterday that I can have both, without installing any extensions.
The key is Firefox's Live Bookmarks. Live Bookmarks track a site's RSS or Atom feed to show you updates as though they were actually bookmarks. In other words, you can bookmark a feed rather than a site, and Firefox will aggregate the contents right into your browser, treating each item in the feed as a bookmark. And it just so happens that del.icio.us generates all kinds of RSS, just like any good Web 2.0 application should, so by live-bookmarking my del.icio.us tag RSS feeds, I now have all my most important del.icio.us links in my browser, and they are automatically updated as I add new links.
For even more Firefox and del.icio.us integration, check out the del.icio.us Firefox extension.