Delicious is a great wiki for teachers to use in the classroom.
It allows you to pre-select which websites you would like your students to view, put them into one list and then give the link to your students. You can choose right down to the exact section of the website you'd like to put on Delicious.
There are also lists you can access, which are already created by others, based on specific topics or themes.
Delicious is a great way to make use of that short Computers period and to make sure your students stay on task, instead of seeing what they might find on Google or other search engines.