Some of our users, like Robert Scoble, can go through 600 feeds in less time than it takes to say "mark all as read":
(Thanks Tim for this video!)
For those of you who don't have supernatural powers and would like a quick and easy way to go through your Google Reader subscriptions, we want to highlight one of our lesser-known features: the "Next" bookmarklet.
The "Next" bookmarklet allows you to use Google Reader through just one link -- clicking on it takes your browser to the next unread item in your reading list (marking it as read in the process). I like to use it to go through my photoblog folder. It's also useful for subscriptions that only include snippets, or when I want to read an article in context.
You can find the "Next" bookmarklet on the Settings page under the Goodies tab. Give it a try, and go from j-j-j to next-next-next!