Lotsa people know about BugMeNot, the centralized database of usernames and passwords for Web sites that require free registration (such as, alas, many news sites). But have you seen the bookmarklet?
On the BugMeNot home page, click on the link that says "bookmarklet" and drag it to your bookmarks/favorites. From then on, whenever you're at a registration log-in page, just click that bookmark and it will pop-up a window with a username and password for the site that you're currently looking at.
The next step will be browsers that automatically log you in to registration-based sites based on a centralized database of free accounts -- so you don't even *see* the log-in screen. I smell an arms race.