I suppose SPI is an option also, but with the above, why bother?
Easy Transfer library from Bill Porter
Here is a link to Bill Porters Easy Transfer page.I found using his library simplified communications incredibly for me between Arduinos. The library is lightweight, easy to implement, very easy to use. You simply define the variables you want to send on both ends, and the library does the rest, including CRC checksums. While I am certain that one could do the same using SPI buses, I found the above to be very robust, fast enough for my needs, and much easier to implement. Since using SPI is so easy for him/her, perhaps smeezekitty can write a SPI implementation of Easy Transfer the same way that Kumy extended Easy Transfer from just Serial communications to I2C.
So my choices are either I2C or SPI basically?