You might want to give zoiper a try, with versions for windows, mac, solaris, linux, windows mobile and iphone (currently pending apple approval). It's stable, fast, multiprotocol and supports video. (Currently only on windows, but we will be rolling it out to some other os'es as well in the near future) Disclaimer: I am involved in the zoiper development. You can find it on http://www.zoiper.com/

Have a look at http://www.zoiper.com/ (disclaimer, i work for them). We make multiplatform softphones with video support (currently only video on mac and windows, we will implement it in our solaris and linux versions later). In combination with an opensource proxy (opensips, kamailo) or pbx (asterisk freeswitch, yate), you can build a very nice conferencing solution, maybe some of your students will even be able to set it up for you. If the university you are working for is non profit, send us an email and we will provide you with free licenses for your students.