Web 2.0 applications for TESOL

Can anyone think of ideas, how to use the interactivity of the Web to enhance TESOL contexts? I'm wondering how blogs could be used, photo galleries, vlogs, social networking sites etc could provide opportunities for students to actually use their language skills.

The following were proposed as possible ways in which forums could be used:

The overall idea was that forums would allow contact between teachers (and their students) in different countries.
- teachers could arrange tasks and activities collaboratively and thus create opportunities for their students to have authentic interaction with one another using English.
- in this way, it would also be possible (in some cases) to encourage autonomous learner strategies, intercultural awareness and perhaps also an awareness of the practical uses of learning English (other than for passing exams).