I had much rather use jigs than minnows but I hear a lot of people do real well with them in the summer time. What luck I've had has either been right before dark when they come up to feed or fishing deep work with heavy brush. I feel they are laid up in there when the sun is shining bright. Seems like you catch a bunch of small fish for every good one during the heat of the day.
You might try casting jigs with grubs along drops that have brush. They can still be caught but you have to work for them. Another thing I try to do is put out a good piece of brush every time I go to sweeten up some of my old spots and add a few more I can hit during prime time.
One of the best things about summer when it comes to crappie fishing is it makes you appreciate fall getting here even more.