Take a look at Mad Magazine in order to get loads of ideas for creative projects that you could assign students in order to help them practice specific language skills and grammatical structures. This issue is a particularly good one: (1991, Summer). Mad super special computer virus edition, 75. Most of these projects could easily be done on a wiki or a group blog.
Low-tech alternative: Take an existing piece of text and remove key words (especially those that happen to match the grammatical structures you wish to reinforce). Have groups of students work together to fill in the missing elements (a la Mad Libs), then assign another group to dramatize the result using the medium of their choice (Legos, PowerPoint, puppets, video, etc.).