There are three entry states for feed readers
In making yet another small mistake with my feed reader of choice, I have come to the realization that there are actually three states that I want entries to be in, in addition to the basic 'read' one. I want to have all of unread entries, entries flagged for later attention, and marked (saved) entries. In fact, I think that this also holds true for email readers, since they are dealing with the same sort of issues.
In theory, I shouldn't need the 'flagged for later attention' state, because I should be completely reading and dealing with each entry and all of its links when I read it for the first time. In practice, this doesn't work out; there are often entries that I can't completely read or deal with at the moment. I don't want to permanently save these entries, but I do need some way to find them later. Right now my solution is to reset these entries to be unread, but this periodically leads to accidents with 'read next unread entry' and other similar things.
(Naturally, there should be a 'read next flagged entry' operation in your UI, and I feel that you should have to explicitly clear the flag instead of having it fall off if you just look at the entry.)
In thinking about it, this is more or less what I do with email too, but with email I have two luxuries not really available in feed readers; I can delete messages outright (and they won't reappear) and I can move messages to other folders. Both of these can be used to turn 'read but not deleted' into effectively 'flagged for later attention', although I think that they're not quite as good as having an explicit state for it.