There's an app called Instapaper that does what you want. They have a Firefox bookmark that you can use and when you next open your app on the iPod it will sync your latest bookmarked articles. You can also set it up to bookmark articles and send them to the app from the iPod's version of Safari which is very nifty since I find it much easier to read longer articles through the Instapaper app than on the Safari browser.
I think this is probably one of the best apps for the iPhone.
Evernote can also do something very similar, but in my opinion the formatting that Instapaper does makes articles much more reader-friendly.
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