The U.S. government has shut down. Sadly, so have most of its websites. No astronomy picture of the day at NASA.gov. No food pyramid guide at USDA.gov. No scanned images of old-timey baseball cards at LOC.gov.
That's the bad news. Now here's the good news: There are two easy methods to try accessing shut-down government sites.
Your first option is Google's (or some other search engine's) "Cached" feature. Enter your keywords, hit search, then look for a tiny green arrow next to the URL of the government-hosted search result that you're interested in. Click the arrow to open a menu, click "Cached", and presto—you get the last version of the page that the search engine crawled.
Sadly, the cached page won't always load images. This is more true for totally dark government websites like NASA.gov than other websites deemed "essential," which are still partially open for business—for example, the weather forecasts at NOAA.gov. Also note that this trick will lose its shine as the shutdown drags on; eventually Google and Bing and others will start caching those annoying "Due to the lapse in federal government funding, this website is not available" screens. (For a depressing gallery of those related to science, check out Jonathan Eisen's gallery.)
If the "Cached" option fails, your second option is the WayBack Machine by Archive.org. Since 1996, its software robots have scoured the Internet and saved copies of the most trafficked websites. You can tap this 10-petabyte-plus collection of website snapshots as long as you have a URL (easily had through search engines).
The WayBack machine is more thorough and burrows several layers into a given site, caching multimedia left and right, but it's not always foolproof, either. The Internet is growing at a faster and faster rate, and the WayBack Machine has struggled to keep up. Another problem related to ever-limited archiving power is that the deeper you click into an archived site, the less likely you are to find cached photos.
But sometimes you luck out. For example, I was able to download this glorious photo of the Eagle Nebula from NASA's September 29th Astronomy Picture of the Day.
Take that, shutdown.