What are the size of the caps you are using to decouple the MCU?
I've got what ST recommends for the STM32F103 part--100nF ceramics next to the power pins and a 4.7uF ceramic next to the analog VDD pin.
You can try the series resistor trick too to reduce the slew rate.
I did! And it works. I put a 1K resistor on the SCK line going to the display and that cut the noise on the power rail by 50%. I hope that a decent layout with a proper PCB will clear up the problem entirely, but for now, since all I've got is a breadboard, resistors will help.
A ferrite bead at each of the MCUs supply pins can help keep high frequency noise out as well.
I was planning to use a ferrite bead on the VDD (analog) supply for the PCB version. You recommend putting them in front of all the mcu power pins?
All of this assumes that the problem you are trying to solve is ground bounce and/or Vcc sag. This could be caused by your SPI bus having a fair amount of capacitance (a lot of SPI devices on the bus, for example.) Driving this capacitance demands large amounts of current which can cause temporary hick-ups in the supply rails. If you can't reduce the capacitance then decoupling caps are what usually solve this problem.
I've only got one device using SPI:
this display from Adafruit. This noise thing is the second issue I've had with it. The first is that while others have gotten it to run at a 10MHz clock, mine seems to get lost at anything over 2MHz. Maybe this is just the breadboard getting in the way again, or maybe there's some problem with my particular copy.