Sitefinity modules system is a bit different from the vendors you mention as they use ASPX files to manage them. Due to this you will not be able to use their modules within Sitefinity. Out CMS system depends on controls for the administration and public part. Therefore you will need to have controls for the administration to manage your modules and controls for the public part to drag and drop them into the ContentPlaceHolders. We believe that this way modules become far more flexible as you define the interface of the content and also the they could be used outside Sitefinity.
Currently in Sitefinity there are three developed modules: blogs, news and polls. We are planning to implement a few more in the near future, probably after the official release of version 3.0. On top of the list are forums and FAQs.