tack:
Just remember that you will need that series cap if using a separate USB>Serial adapter, if it doesn't already have one; e.g. most PL2303 or CP2102 modules.
A little clarification there - it is not the USB to TTL adaptor that has the series capacitor, the FTDI adaptors certainly do not have one. The capacitor becomes part of the interface on the ATMega board to whatever adaptor is used.
What the "bogus" PL2303 or CP2102 modules lack is having the RTS line brought out to the interface pins. On the six pin versions which were apparently put out by some poor sod who simply had no idea what he was doing, it is possible to modify them with some track-work to repair the blunder, but this has nothing to do with the capacitor; you do not add the capacitor to the USB to TTL module, it goes on the MCU board.