For synchronous communication, there are many options. As an instructor, I can use a chat tool within our LMS, I can use a tool such as Elluminate (now Collaborate) to hold class sessions or host a group meeting or hold virtual office hours. Any of these would add to the interactivity of a course. I think each would have its place.
For example, to enable students to “chat” with me in real time, I could use a chat program that stands alone outside of of the LMS to allow students to reach me without needing to go into the course. I use iChat but also use Meebo which allows me to sign into to multiple chat accounts and manage them through one platform.
To bring a group together for teaching, a group conferencing tool such as Collaborate would work well. This tool could also be used to host small-group meetings or office hours. This type of synchronous tool could also allow for students to teach or present projects to the class.
For our class, I chose to participate in a Moodle Chat session with the instructor and another student. I selected this option because I am not that familiar with Moodle and had never used its chat feature. There really wasn’t much of a learning curve (both because the tool is very simple and because I do “chat” often). It was very easy to use and quite simple. There were not a lot of bells and whistles, although you could “beep” each other which sent a text message to the person and loud audible BEEEEEP. We all agreed that would be great for multi-taskers who may be chatting along with several other activities at the same time.
For a short video explaining how to use Moodle Chat, see this video.