What is the best tool for my EFL students to improve their writing: the wiki, blog, Moodle, or facebook?

What is the best tool for my EFL students in order to improve their writing: the wiki, blog, Moodle, or facebook?

Hello Webheads,

 I just found this site and can see that it is going to be a valuable resource and reference for people on my site at Mexico English Teachers' Alliance (META Web 2.0).

I am really interested in elevating English language learning (ELL) in Mexico via technology. A brave and bold target here, but very important. So if there are any Webheads that want to participate in this important project, please stop by and comment or help out. We really do need Webhead voices to enrich our efforts here.

Ok, I've finally made it - after taking an on-line course 'baw07' this winter I came to the website itself!!! Feels like in the very beginning of the course - so much information. But I'm sure I'll make it :) I wonder how much time it will take for me to feel completely comfortable in this stream of information?