there are a few sites that have short videos or animations of some medical procedures. i have mostly seen animations of the heart. health centers online has several sites focusing on diseases, diabetes and the heart the most common, where they have short animations. you can access their other health center sites on a link at the left side of their webpages. you may have to register to get into more than one or two pages on their sites, but the registration is free. another site that has short videos is the health scout network which has archives of those short 2 or 3 minute vignettes that play on tvs in doctor's offices while you are waiting to be seen for your appointment.
i imagine if you have internet access during a presentation these could be accessed and displayed to a group. medline plus has a number of tutorials and also videos of procedures, but most of them are aimed at the general education of the public although they have good information and are based on medical procedures. check out their site: http://www.medlineplus.gov/
you can get a list of the videos and interactive tutorials by going to their site map page.
the one public access site (central ohio technical college) that had their nursing videos online has made them password restricted to their students only. one iv team i was on made a video for our hospital. it is doable as long as everyone working on it works together. you might consider writing your vignettes and having someone from the school av department filming and editing them for you and placing them in a computer file. your filming sites could be the school nursing lab, or even a local hospital room with the hospital's permission.