ERNLLCA (East Riding & North Lincolnshire Local Councils Association)
ERNLLCA have produced a Basic Councillor Induction video which can be viewed here.
A full transcript of the video is available here.
The ERNLLCA Councillor Induction page can be found here (login required - details available from the Clerk).
NALC (National Association of Local Councils)
NALC publish Local Councils Explained.
They also offer a ranger of "Good Councillor" guides - here are the main two from the selection;
The Good Councillor's Guide
The Good Councillor's Guide to Finance.
East Riding of Yorkshire Council
ERYC provide a wealth of parish information on their Intel-hub.