A super nice member!
Google Sites was used to increase communication between students at our college. Each course had a representative, but they were spread across multiple sites, so didn't meet up too often. One of the students volunteered to create a central site (working with Student Services) to provide an online place for class representatives to communicate and pick up information. The student then trained the Student Services staff how to use the system.
Strengths and weaknesses? There are two ways to use it, either through personal accounts or through your organisation having a Google Apps account. In our case, we chose to set up an account for the organisation, so each student had an email address under the college domain name. This was a huge strength, in that not all students had college (.ac.uk) addresses and it also gave them additional storage space and an online 'office' suite of applications. From another viewpoint, this is a weakness in that it requires setting up by your organisation with all that may entail.
All sites can be set up for the group involved, and can be shared and made as open (or private) as you require.
I would recommend Google Sites wholeheartedly to any colleagues, especially if they then move on to the possibilities of collaborating on documents/presentations/surveys. You're in the 'cloud' with a minimum of fuss…
Ratings – the learning curve will obviously be very different if you use individual accounts or an organisational Google Apps setup.