CrossRoads:
On a '328P based card, 11-12-13, MOSI, MISO, SCK - are connected to the ICSP header.You don't gain any pins.
Since they are the SPI pins tho, you can connect other SPI devices in parallel (like an SPI based RTC (vs I2C) ) and control it with another chip select line.
A4/A5 are the I2C pins.
All the analog pins can also be used as digital pins (A0-A5 are D14-D19).
Yeah, I was aware of the Analog pins able to be used as Digital, as well as the PWM pins being able to be used as Analog. So, I don't gain pins, and because of that, I would assume if I have say an SD shield hooked up to ICSP and nothing on 11,12,13, SS, that I wouldn't be able to use those pins individually for anything else. For instance if I wanted to use the LED on 13, it would interfere with the ICSP. Sorry if that is just repeating what you just said, I just want to make sure I understand so I'm on the same page with no confusion.
Obviously, the SS pin would have to be dedicated to that shield I'm trying to use.