If your students have worked collaboratively to create a learning product through a small group wiki, then why not have them present their product via the same wiki? They already have the information from all of its stages -from brainstorms through various drafts. They can copy the information to a clean wiki page and organize it. They can either link to other presentation pages or they can move all information to one long scrolling page (put in about 12 blank lines between each aspect so that each aspect shows up by itself on the screen). They do not have to go to PowerPoint to do their presentation.
This type of presentation is especially good to demonstrate changes in thinking, growth in the project, and increasing levels of complexity. Students can show parts of their early brainstorm and then show their final product. They can show the various decisions that the group went through. Group members can add their feedback to each other and any teacher feedback and show how that feedback was incorporated to create a better product.
Have your students used a wiki for presentation?