What value capacitors should I use for a 65C02 and 28 series EEPROM? Thanks!

I built Rich Cini's design (http://www.classiccmp.org/cini/6502proj.htm) and he uses 0.1 uF ceramic capacitors for decoupling.

Note that not all ceramic capacitors are created equal. Some have excessive ESR and/or ESL, which will compromise the capacitor's ability to bypass the high frequency noise generated as devices change state. Garth Wilson and I recommend the use of MLCC types with an X7R temperature coefficient, rated at 0.1 µF at 50 VDC. I built POC V1.1 with AVX MLCCs and have gotten good results. These capacitors are quite inexpensive, so there is really no good excuse for not being liberal with them.

Each device should have one such capacitor, with it installed as close as possible to the Vcc pin. Keep the leads as short as practicable for best results. It's also a good idea to place one of these capacitors as close as possible to the point where Vcc enters the board, along with a low ESR electrolytic of at least 100 µF (500 to 1000 is better) at 10 or 16 volts (10 is better, if available). If the board is fairly large another electrolytic should be placed at the "other end" of the Vcc/ground distribution, along with an MLCC.

The seemingly high MLCC voltage rating has to do with a characteristic in which the capacitance rapidly degrades once the working voltage is exceeded. Although most of our circuits operate at a nominal 5 volts, ringing and miscellaneous transients can cause voltage excursions well in excess of Vcc.

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Why is 10 better than 16, BDD??

Some electrolytics won't produce their rated capacitance if the working voltage is too low relative to the capacitor's rated voltage.

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

So, both too high and too low reduce the effective capacitance?

The effect on capacitance when the working voltage is well below the rated voltage seems to vary. I don't think there is a hard and fast rule on it.

Naturally, if the working voltage exceeds the capacitor's rated voltage a breakdown may occur and cause a catastrophic failure. My practice has always been to limit the working voltage to no more than 85 percent of the capacitor's rated voltage.

_________________
x86?  We ain't got no x86.  We don't NEED no stinking x86!

I use 100nF (0.1uF) MLCC ceramic capacitors rated at 50V as well. Does the job, especially if using one per IC.
I also tend to use 33uF Tantalums every 5th IC (or so) to deal with any largish dips in the power rail. Tantalums are quite goods for this as they offer a fast reactance with a decent capacity rating. Down side is that they are more expensive by quite a bit than electrolytics.