I use web-based multimedia for lectures using some Java (TM) Applets that I developed: SoundButton, ManualShow, and AutoShow, where the latter two are full-screen slide shows. Download the java classes here: classes.tar.gz and peruse the quick-reference card here: README-FREEWARE.TXT.
(Working over modem? Wait a minute or two for the loading to finish.)
Included with the applets is another version of this slide called "AutoShow" that plays automatically without the need to press "next" all the time.
SoundButton, ManualShow, and AutoShow were originally written for teachers and professors who give lectures in multimedia classrooms where the computer screen is projected onto the wall. WWW delivery is especially nice in this situation because students can access the lecture material later (say, midnight the day before a test) without calling the instructor! Also, Mac lovers or Unix geeks need not worry that the computer in the classroom is a PC, the slide show will still shine.