During a simple project, I found that there were not any bundle providing the Multiple Step Form feature. Actually, I found one, https://github.com/craue/CraueFormFlowBundle . But for me, this bundle focuses too much on the Forms themselves, which was not relevant to me. For instance, I don't use to handle Form Event. Then, I came to the idea I could create a bundle which let developper interact with each form separately and then use a little well-configured system to manage the set of forms, the transitions between them, hydratation, ...
Therefore I created the MSFBundle. It's a little one with currently 5 or 6 classes and works out as a service. Its usage is very similar to form themselves to reduce learning time.
Bonus : with this system, it's easy to manage transitions even between MSF. You just have to configure actions at each step.