Although Parallels supports Solaris 10 in its virtual machines there are some minor issues with 1280×800 resolution of Macbooks.
Jean-Christophe Martin published a workaround for Parallels Desktop build 3036 which partially solves problems:
Create a new VM with the Solaris 10 type, but, before to finish, un-select the option to start the Solaris installation and edit the VM configuration to add a custom screen resolution of 1280×800.
Start the VM to launch the install.
Log in an create a /etc/X11/xorg.conf with something like the one attached here (xorg.conf). Basically you need to add the Modeline lines (generated with /usr/X11/bin/gtf) and put 1280×800 in the appropriate Display subsections.
Check the original post for updates and comments.
BTW: Glenn Brunette, Distinguished Engineer and Director, Global Sales and Service Security Office at Sun, took a nice screenshot of Solaris 10 with Trusted Extension (11/06) running on Parallels Desktop.