Power on reset circuit for microcontrollers
If you want a reliable power-up reset, a simple RC is not the way to do it. 

The capacitor you suggest (plus a diode across R1 to discharge the capacitor when power is removed) will sort-of work most of the time, and some crappy products actually use something like that. 

Instead it would be better to use a supervisory circuit such as an ADM803 (open drain output), which combines a voltage reference and comparator that work down to a low supply voltage with a RC timer that produces a reasonable length reset pulse when the supply voltage reaches or recovers to an acceptable level. I also don't think much of using the diode rather than a gate- it does not guarantee a proper TTL low level even with a switch, and that issue may cause problems (perhaps immediately, perhaps at low temperatures) when a reset circuit is used since the reset circuit won't pull the output quite as low as a mechanical switch will. Using a push-pull supervisory circuit (ADM809, IIRC) and a quad NAND gate (connected as two AND gates) with the two mechanical switches would make it all kosher (or halal).