Where to find latest videos of colloquia or other talks in your field?
Mathematics

From my experience not very many schools record talks as a matter of policy. But the special institutes often do. 


MSRI has videos available for workshops dating back to at least 2004. 
Fields Institute also has a large collection.
Newton Institute records almost all of its seminars and colloquiums. 
IHP has a Youtube Channel, and if you follow them on Google+ you get updates (sometimes even hourly) on new videos. 
Clay records their research conferences. 
Simons Center for Geometry and Physics no longer maintains a central list of videos. But if you visit the individual workshop pages the videos are made available very soon after the talks. 
QGM (Centre for Quantum Geometry of Moduli Spaces) records their conferences and master classes.
Banff International Research Station (BIRS) makes conference/workshop videos available.