It would seem that you duplicated the 5 V and 6V designs, and just added 8, 9, 10, 12 volt outputs.
You'll notice that the resistor for the 5V and 6V outputs is 1K ohm. This is because the 78xx series regulators need a minimum 5 mA load current. So the 5V and 6V outputs have a 1K ohm resistor which gives 5 mA and 6 mA minimal load. But you duplicated this all the way up to 12V, which is not necessary, because then you have 12 mA load at 12V. You just want to have the 5 mA minimum load at each voltage, so for 8V, the load resistor can be 1500 ohm (8/1500 = 5.3mA) ,for 9 V you can use 1800 (5 mA), for 10V you can use 2k ohm (5mA) and for 12V you can use 2.2k ohm (5.5 mA)
So that means
R3 | 1.5k ohms |
R4 | 1.8k ohms |
R5 | 2k ohms |
R6 | 2.2k ohms |
If I were to make the design below, I'd also add a small electrolytic capacitor after each linear regulator, something in the range of 10-100uF 25-35v would be perfectly fine.
This is a good idea, but you will also need to add a diode from output to input, because adding output capacitance risks having the output stay at a higher voltage than the input voltage when you power off (especially if you also lower C1, C2, C3, C4 to a single 1500 uF capacitor as suggested).
Suppose you have high loads on each output except the 8V output, which is unloaded. Then the 10-100uF cap on the output of the 8V can hold-up the output voltage when the input voltage falls off(due to the other loads, it will fall off fast). This will guarantee damage to the 78xx voltage regulator. So to counter this, each regulator should have a protection diode from output to input. This allows the higher voltage at the output to bleed back and bypass the regulator's internals.
EDIT: I'd probably keep the output capacitance at 0.1uF as you already have, and just put the 10uF at the input. Keep the bulk 1500uF capacitance at the supply end near the bridge rectifier. I've drawn this below for a few voltages. Also, I put an RC snubber across each diode of the bridge, this is a good addition if you plan on using your PSU for any audio work. It removes the switching transients on the diodes. If you don't care about audio work, then you can leave the snubbers off.