Hermann's is by far the longest-standing jazz venue on Vancouver Island.  It used to be a little tacky, but was refurbished after a fire in the building in the late '90's and is now quite presentable.  It is a friendly, relaxed place that features all kinds of jazz every week ... it is open most evenings as well as at various other times, especially on weekends.  Hermann's website includes an online event calendar; click on a listing there, and a mini-window will pop up detailing the event. 

It is in the downtown core so walkable from most hotels; street parking can usually be found at night, and there is almost always room in the city parking garage a couple of doors down View Street.  After coming through the front door, you go straight ahead along a corridor lined with posters of jazz concerts.  In the club, you can sit at the bar or at a table.  Just make sure there is no pillar between you and the bandstand.  Drinks are reasonably priced.  You can drink Hermann's beer, but it's a different Hermann! :-)  Food is also available—check the TripAdvisor reviews.

The Thursday night lineup is a fixture: the Esquimalt High School Jazz Band at 5:00 pm, no cover charge,  followed by  the Tom Vickery Trio at 8:00 pm, $6 cover.  The Monday Night Big Band plays a couple of times a month at 8:00 pm, cover $10, don't miss this one.