Your question is very hard to answer with any meaning without a whole lot more information. What do you mean by asynchronous? What will the emphasis be on activities. For example if you anticipate significant use of video or large numbers of students taking exams simultaneously the solution will be very different to most installations where the emphasis is on uploading and downloading fairly small documents. It will also depend on what technologies you are comfortable with/currently using.
What has your searches returned so far and what questions do you have on that information.
