Q. This past Ramadan, there was one time after Taraweeh we had a group tasbeeh and you told us before starting it that those who are of the opinion that this is Bid’ah, they’re welcome to leave and a few people at that point did leave. Anyways, I was listening to a scholar who said that saying “Allahu Allahu” etc. in a group chant is a huge form of Bid’ah and said that our beloved Nabi (SAW) never did anything like that. He said that this type of Sufism is completely wrong and anyone doing such an action has a grave punishment awaiting for them for they started something that the Prophet (PBUH) never did.
The reason I bring this up now is that this particular person is world-renowned so I would just like to know what the Ulama (of the world) have said upon these practices.
Because for me personally, when I was a part of that, it felt amazingly spiritual given it was in the masjid, late at night, in the blessed month of Ramadan, and there were throngs of people which helped create a sense of unity.

Q. Is their azkaar after salah?

Answer:

1. The zikr you have mentioned can only be viewed as a bidah for that individual that believes that such a remembrance of Allah happens to be the only way to attain His pleasure. That no other way exists to make Zikr except this given way. To occasionally do it to show people the significance of zikr, and different methods of performing zikr is not bidah. Such an action would be part of sunnah. At moments of prayers, it would be recommended that such deeds be done out of the musjid sphere so as to not disturb those that wish to do other forms of ibaadah.
2. Bidah has many levels to it. Some acts of bidah are close to shirk. Such actions would be forbidden. The bidah of zikr is part of bidah-e-hasanah.
3. Hadeeth proves that the recitation of azkaar after salaah is an action very much part of sharia.  To teach people of its significance is also part of deen. Although it would be best that people make such zikr softly, or in a place of their choice (out of the musjid) so as to not make the act of zikr into a mockery, such actions performed occasionally can function as an inspiration to those that do not know how to perform zikr, or refrain from it out if sheer ignorance.
4. The scholar would be correct if he is not opposed to such a practice on an occasional level, for reasons outlined above, otherwise his vehement denouncing of it can also function as a bidah.
5. Zikr is not limited to sufis. The scholar would be correct to state that to impose such an act would be wrong. We too would agree that to impose this form of worship would be incorrect.
6. How does this scholar define ‘huge bidah’ as opposed to a small bidah? Does he sanction only small actions of bidah? If so, what are they? Reciting the Quran is also a form a zikr. It is a practice that exists in many of the major musjids around world, including Makkah and Madinah. Would it also be stated that people memorizing the Quran in an audible manner in group setting are conforming to bidah? Attending the modern college environments, usage of cars, computers, airplanes, e-books, recordings of great scholars, etc. are all actions of bidah. Are these the works of sufis as well? (The answer he gives to sanction these behaviors can be the answers of sufies answers as well!!!)
7. We must be cautious of how Bidah is defined. To define it haphazardly reduces our understanding of religion.
8. Because a thing feels good does not justify its everyday public occurrence. Sometimes shaytan makes us attack a group with the false impression that we are defending religion or are more superiorly religious. Shaytan makes us do wrong things whilst giving us the false perception that we are making religious strides and are united despite us being in conflict with the sharia. We should not be fooled by the ploy of shaytan.

Allah Certainly Knows Best.

Also see: http://islaminaction.wordpress.com/2008/11/03/bidah-according-to-imam-nawawi

http://islaminaction.wordpress.com/2009/01/17/duaorzikraftersalah