Here you can find some things relevant to rats that interested me while browsing and I find them interesting for you too.
If you wonder how to keep your rat clean, I have one amusing tip for you. RATBEHAVIOR.org offers an elaborate plan how to make clean and soft creature from your little piggy :D
World through the eyes of rat
RATBEHAVIOR.org offers great amount of interesting information. For example, there is an article describing how rats actually see. And for better imagination, you can watch three videos, see link below.
First video shows you the world through the eyes of normal rat, second displays the same through the eyes of albino rat and third is the original human video.
Gallery of rat diseases
This link is published only for practical purpose. Website MOUSINI.com gathers pictures of rats suffering from various diseases and problems, such as tumors, overgrown teeth or parasites. It is not easy to look at, so if you find yourself too sensitive rather skip this link. But it is quite possible that you will have to face some of those problems one day, so maybe this gallery will finally help you.
Added another link.
RATZENET.de enables to watch rats in their cage online. Most of the time they sleep but I managed to see them a little bit more active. Don't be dissapointed if you don't see anything for the first time and try again later, some lazybones definitely come up:) The owner states on the website that the feeding time is 10 p.m., so at that time there could be more activity.
Wild rat in Prague underground
IDNES.cz published an article about Prague sewerage celebrating 100 years. There were many interesting pictures and videos. Among others following video of a romping rat.