That's a good idea. I met a salesclerk one who spoke English very fluently. I asked him for tips on learning English well, and he said that he learned a great deal from SecondLife. Since the operating system and chat is all in English, he was motivated to pick up the language and use it correctly to communicate with others and to experience the "flow" of the game optimally (see Csíkszentmihályi). Although his primary goal was the playing experience, he learned effectively and with a high level of motivation, genuine feedback/reinforcement, and collaboration/interaction through the SecondLife forum.
Here is an article "Diigo在華語教學上的妙用." It briefly introduced what Diigo is and how to use it as an instructional / learning tool. Hope it can help you to apply Diigo in class.
Just a summary of a few of the better comments from this Voicethread:
1) literacy - collaborative story writing; sharing and reflection on writing; peer review and feedback; book reviews; with younger learners, picture book comments
2) foreign language learning - recitation and practice of pronunciation, commenting on a picture (focus on tense, fluency, or listening comprehension)
3) Thinking skills - brainstorming, problem-solving, word-problem solving (maths), critical thinking/reflection
4) distance education - contact with sick students/sick teacher
5) professional development - creation of presentations for promoting web 2.0 apps; use as an action research collaboration forum
I had the chance to see one of our classmates use this technology with a teacher in Taipei for fostering English language skills. The students were asked to plan a trip to a foreign country, including how they were going to get there, their travel plans, lodging, and potential problems they would face. They were asked to solve those problems and make a conclusion for their presentation. They presented in groups of two, using pictures from the internet and recording their voices for each slide. I listened to each presentation and provided detailed written feedback in terms of vocabulary, pronunciation, fluency, comprehension, and grammar. The teacher said that the students were excited and encouraged to have this kind of feedback and worked hard to finish their project and make recommended improvements. Their motivation and attitude of the project were both good. However, the authenticity of the final product was somewhat limited by the fact that their Voicethreads were private, for privacy concerns. Nevertheless, I see the benefit from this activity and hope that the example provides some insight.