Scotland don't necessarily have to do anything tonight (I can't see them getting anything from Spain) - Czech's are poor and unpredictable, and they play Lithuania in Vilnius, having lost to them already at home. Lithuania have been relatively decent in the recent past, not threatening to qualify or close to it, but pulling off decent results here and there, and it's not beyond possibility that they'll cause a shock tonight against the Czech's. This would in turn lead to your shock referenced above Geysir.
Belgium is a really intriguing one. They have the makings of a fantastic, truly world class team in place at the moment. All they need is a bit of big game experience. To go to Germany and win is about a tough a prospect as they can have, but they'll have to do that. They have the players definitely, but they've handicapped themselves by some strange results in the group. A long shot.
Armenia we know the story.
My money is on Estonia. They don't have to worry about their own game, they've the points on the board and are winning the head to head. Serbia must win in Slovenia. A derby. They've been erratic, but perhaps the play-off all-or-nothing nature of tonight's game might focus their minds. Don't see it myself.