OK, linux and solaris, what fun. Basically, what I would do is install Solaris first, and then use the same partition table for Linux. So, in other words, your swap partition is your Solaris swap partition, and the boot partition is the same. What distro are you going to use (linux)? Now as for grub.conf, this
is the best guide I can think of. Basically you'll have to copy both your linux and Solaris kernel into the boot partition, and then setup two different options. Let me know what distro your using, and I'll see what I can tell you about how to take it from there.