The last missed reference also comes to us from the contributors to Memory Alpha, who noted a Shakespeare allusion in Season Six. Q reappears—and this sort of thing always seems to happen when Q appears—in Captain Picard's afterlife.
And Shakespeare is there, too.
More specifically, a line Hamlet delivers—"When we have shuffled off this mortal coil . . ." (III.i.66)—is re-delivered there, Q making one small change to Hamlet's line, substituting "the" for "this."
And there you have it! All the Shakespeare in the Star Trek universe—or all the Shakespeare I've been able to find in The Original Series, The Animated Series, The Next Generation, and the films. Beyond that I decline to venture. At present.
Links: Shakespeare and Star Trek Complete.