Apart from museums and galleries it is hard to keep a regular update of events. Unfortunately, the sites that have taken on this task such as the web site of the Municipality of Chania don't seem to bother with updates any more so you will have to find out once you are in Crete by asking around.
The standard way to list things happening in Crete is still to post signs on walls (generally at very short notice) in the cities. Also if you read Greek you can see the Xaniotika Nea newspaper (for Chania).
Museums are the main repositories of culture in Crete and where most visitors head for when wanting a little bit of culture, if only because it is easier to find them than other cultural events and exhibitions.
Galleries there are a few galleries in Chania listed below
Cinemas in Chania. Films are always shown in original version with Greek subtitles (with the exception of children's films which are often dubbed)
Theatre and plays are sometimes shown in Chania and other cities but almost exclusively in Greek language
Music: there are concerts, especially in the summer, but the main place to listen to Cretan music is at feast such as weddings, baptisms and village feasts.
Traditional Cretan entertainment is almost always related to weddings or baptisms and will involve eating, drinking, listening to traditional music and dancing for most of the night. You can also see tourist versions of these feasts provided by tour operators and which often go by the name of "Cretan night".
Another form of traditional entertainment is provided by watching people do their "volta" - literally the "turn". This consist of slowly walking up and down the main street (or other area where people congregate) to see and be seen.