I like the way bloglines (
http://www.bloglines.com) handles things (purge after reading). This would mean you store a "last read / purged on" column to each subscription (I guess...:)) and only display items (from the sources) where the source timestamp (if there is such a thing...) is newer. For new subscriptions the last read /purged on will (obviously) be NULL, therefore all items for this subscription should be displayed.
Not having looked at NA, does it support folders and if not, would you consider adding them (so we can store subscriptions in folders). Also, does it interface with categories? (I imagine having the ability to subsribe to a new source and add a category to it, if the default category given by most users does not suit my (personal) needs).
