Here's a very brief and imperfect description of each I made:
A. Secular Mindfulness movement
In this form people use Buddhist techniques for improving mental, psychological well being and may also use Buddhist mindfulness in a corporate setting, known as "Corporate Mindfulness." Those who follow this form may not even meet at a temple and might meet online, in an office, or in a yoga studio. Belief in rebirth is optional and most are at least skeptical of rebirth and generally don't follow many Buddhist practices other than meditation.
B. Meditation center Theravada / vipassana
In this form the members practice vipassana and other forms of Theravada Buddhist meditation at lay, peer-led groups and retreat centers. They might meet occasionally at Buddhist temples, but mostly meet at yoga studios, rented facilities or each others' homes. Typically there is a leader of the group who is a lay Dhamma teacher who might also have a regular full-time job and teaches and leads the group during his/her times off from work.
C. Traditional Temple Buddhism
In this form, Buddhism is practiced at the temple and includes Refuge and Precepts ceremonies, Poya and Upsosatha day activities and other generally religious practices including blessings, funeral chanting, etc and all temple activities are performed by ordained monks and nuns.
D. Modern Theravada
In this form the focus is on the Pali Canon, especially the Suttas. Those who follow this are sometimes referred to as "Suttanta." They might still hold the Abhidhamma and Commentaries in some regard, but their main focus of study and practice are the five Nikayas of the Suttas. The members of this form are Buddhist, generally accept rebirth and simply focus on the Suttas rather than what they feel are some of the later writings and teachings.
E. Classical Theravada
In this form, the Classical Theravada Buddhists hold the entire Tipitaka in highest regard along with Buddhaghosa's Path of Purification and all the other Commentaries of the Elders in very high regard. They tend to take a more literal interpretation of the texts and strong adherence to the Vinaya.
The above is just a cursory overview and of course there can be some overlaps in one or more of the above forms showing up with some practitioners.
(modified, updated from an original list by Dr. Gunasakera)
http://www.theravadabuddhism.org/