An unfortunate side effect of having your blog or Web site hit by sudden, massive traffic of the type you get when linked to on sites such as Digg, Del.icio.us, and Reddit, is downtime. While bad for the person who owns the site, it's also the pits for people who want to get at the content and can't. There are services such as Duggmirror, and Google's cache to bail you out, but otherwise you're out of luck. Mr. Uptime is a new Firefox extension from the folks at Pingdom that lets you earmark downed sites, and return to them later when things are back to normal.
Once installed, if you hit a site that's down, the Mr. Uptime toolbar will automatically pop up. You can hit one button to bookmark it for later. Pingdom will keep an eye on the link until it's back up--or as long as you set it to look--then open it in a new tab or window on your browser. You can also set it to give you a small alert.
This is a great tool if you're a frequent user of social-bookmarking services and run into these dead links on a daily basis. It's also helpful if you're waiting on a more critical service such as a banking or commerce site. Otherwise, you're probably better off exercising patience.