Sound

Soundsnap
I’m not sure there’s any better site. Do recommend it to me if you have one. Soundsnap’s appeal comes from the variety of sound clips and ease of use of the site. You must register and you’re only limited to 5 downloads per month but it has a paid version. I never needed more then 2-3 sound effects before so this site works for me.

Video

Zamzar
Since powerpoint can’t play .flv files directly, you can convert the video using online converters. Get the URL from youtube, paste it in this site, select format as .avi, put your email and zamzar will send the file to you via email. Don’t expect the files immediately though.Last time I tried it took me 4 hours.

If you’re a designerholic you would have seen multizillion pages like this already. But this one is special as its a reference for me and my beloved students.