The SZ has an excellent info graphics which includes all relevant pollsters. I will base the following on that. First up the parties which are in the current Bundestag:
- CDU/CSU (Union - black): the centre-right parties have been above 40 % for most of 2013. Merkel is by far the most liked politician in Germany. She will probably be chancellor for four more years. The CSU is the Bavaria only "sister party" of the CDU. They managed to win back the absolute majority in the state last Sunday.
- SPD (red): the centre-slightly-left leaning party is the second strongest force in the political spectrum; they are trending at around 26-28 % . Chancellor candidate Steinbrück was able to improve his standing in a "TV Duel" with Merkel significantly. Germans were asked whom they would vote for if it were possible to elect the chancellor directly. Before the "duel" only 22 % would have chosen Steinbrück. 32 % would vote for him today. The party was able to gain, which is primarily due to a weakness of the greens.
- Grüne (actually Bündnis 90/Die Grünen - green [obviously]): the centre-slightly-left leaning party with a strong emphasis on sustainability and civil liberties is currently being favored by around 8 % of the electorate.It has been falling this month from around 13 % primarily due to a possible involvement of some party leaders in a push for the legalisation of pedophilia in the 1980ies, which has just been made public. Also, the party wants higher taxes, which also negatively affects their polls.
- Die Linke (purple): the left wing party reaches poll results of around 7-9 %. It was founded in 2007 in a merger of the east German PDS and former SPD members (WASG), who left the party due to the Agenda 2010. It was also able to profit from the weakness of the greens. The party is becoming more and more euro sceptical, because they see the currency as the primary reason for the abolishment of the welfare state which is currently happening all over Europe.
- FDP (yellow): the market-radical liberal party is in danger of falling below the 5 % hurdle in polls (trending somewhere between 5-6 %). In Bavaria only 3.3 % voted for them, which scared the party into trying to run a borrow-vote campaign. They urged the CDU voters to help the current coalition by giving them the second vote. Germany has a dual voting system in which the first vote is given to a candidate and the second for a party. In the past borrow-vote schemes did not damage the stronger party much, but helped the weaker one. This was unconstitutional so in the new voting law the stronger party loses more seats. The CDU/CSU is having none of it this time.
- The Pirates: the party (currently at 3 % - orange) - concerned mostly with freedom online - was not really able to profit from the NSA revelations. It seems unlikely that they will be in the next Bundestag.
- AfD: the newly founded liberal, euro-sceptical, party (blue) is currently at 2-4 %. But pollsters don't trust their own numbers here, because protest voters decide shortly before the election whom they will vote for. There is a chance that they will get over the 5 % hurdle, and some polls are seeing them at 5 %.
- Union/FDP: Merkel claims that she favors the current coalition. It seems rather unlikely that she really believes internally that it was a success, since constant fights between CSU and FDP, basically forced the government to stop governing in 2010 (one year in). Next to nothing has been achieved(yeah Merkel is only big on reforms - elsewhere). Still, it is quite likely that we will see four more years of this. If we believed what politicians say before elections, then it would be one of two possible coalitions at this time since the SPD candidate Steinbrück has ruled out a grand coalition.
- Union/SPD: no matter what politicians claim before an election, I think this is the most probable coalition. But the SPD is likely scared that a grand coalition will damage their brand (which the last grand coalition did), which is already very similar to the Union's. Still, when push comes to shove, it is more likely that Steinbrück will step back, and thereby making a coalition with Merkel as chancellor possible. 47 % of the electorate would like to see this coalition, according to ARD DeutschlandTrend.
- Union /Greens: neither the Greens nor the Union like the idea very much (only 21 % think this would be a good coalition). Merkel called it a "figment". But there are more similarities than differences; especially after Merkel changed course in the question of nuclear power. So, even though it is not the most probable coalition it is possible.
- SPD/Greens: wishful thinking on part of both parties. Very unlikely they will have enough seats. But see below, for a possible option.
- SPD/Greens/Linke: this might be possible, but, big but, the SPD considers the Linke
traitors(many left the SPD) dissenters, who are not fit to govern. On state level this coalition is not unheard of. Still, this is one of the few times, where I actually believe, that politicians tell the truth. So, even if it would be a possible coalition it seems unlikely. Perhaps we will actually see a minority SPD/Greens government, which is tolerated by the Linke. That would not be a stable coalition, but it is far more likely than a Die Linke minister.
- SPD/Greens/FDP: would be the stupidest idea ever.