I haven't spent a whole lot of time odeing this summer so far, but I have come across a couple of lifer damselflies. Both these species are found in rivers in Southern Ontario.
The bluets (Enallagma) can be difficult to identify, with many species differing only in the shape of the reproductive parts. River Bluet is a little easier than some, with a narrow, tapering shoulder stripe and the long upper clasper (on the tip of the abdomen).
In general, the Ontario species of dancers (Argia) are found in rivers and large lakes, but there are exceptions. This is a Blue-fronted Dancer, one of four dancers restricted to Southwestern Ontario (two other species are widespread).