The easiest way to do it (as far as i know) is click on file in the top left corner of the i-tunes screen and select create new playlist. One should then appear down on the left hand side of the screen. You can then rename this playlist by right clicking on it (I think) and you could call it "recently added". Then all you have to do is click on Library and pick out your recently added ones and drag and drop them into the recently added playlist.
I'm no expert on i-tunes so someone else might come up with a better idea.
Hope this helps.
Live long and prosper.
The needs of the many outway the needs of the few, or the one.