In addition to D.R. Zandee's suggestions,
consider Moraine lake, right close to Lake Lousie. Even smaller, but more picgturesque in my mind. Can dirve almost to the shore (you can rent canoes there to). T.the 10 peaks and the lake were once featured on our $20 bill.
Worth a part day trip if you are camped in the area for Lake Louise already.
You may want to avoid the lakes to the south of Banff that are Damed. (Upper/Lower Kananaskis, Barrier, Spray, etc) The shores tend to be kind of stark, with cut stumps, and if the water is low a lack of vegitation near the water line... The mountains and suroundings are still fantastic.
Lake Miniwanka is an exception to this suggestion.
Some pictures I've taken from a few of the Calgary/Banff rivers and lakes are at:
http://www.members.shaw.ca/myrlskayaktr ... trips.html
One day I'll clean up the text...probably not worth reading, but some pictures may help you with deciding which to go to.
Last Saturday (July 24)I was out to Upper kananaskis, the campsite on the far side of the lake from the road had lots of room (canoe, boat or hike in only). I every campsite sign I saw on the road said "full". So best to reserve.
Sunday I went to Lake Louise and Moraine... could not even get to the parking lots, as we were being directed to park on the side of the road. The morane like person let me through so I could drop off the boat (and by luck, I did find a spot closer as someone had just left)
regards,
Myrl