I run distance-learning on-line courses, and as part of the package, students have tutorials (about 20 mins per unit) via phone or Skype. Each tutorial is closely based on what they've been studying - there are a set of questions, conversation topics etc for each unit. Written practice is also given via E-mail. They can also contact me anyway they like if they have any problems - if they're not sure how to use the programme, have a grammar query etc.
Obviously, Skype is cuts out the cost of the phone calls and is a better option in particular for anyone a long way away. It also has the advantage that with the webcam added they can see me - a lot of students feel inhibited about talking on the phone without being able to see who they're speaking to. adding the webcam sometimes detracts from the sound, but even if it's only on for the first twenty seconds, it helps.
I wrote a couple of articles about these courses - you can find the first one
here. Or if you want to see the courses themselves go
here.