Don't you just love ssLauncher for that option? What I tried to do is have widgets or the most important apps on one orientation and then the less important on the other. Grouped by multimedia, news, games etc.
http://xdaforums.com/showpost.php?p=37952345&postcount=875
I'm basing what goes in whatever orientation on whether I'm on the go or just standing/sitting in one spot. I prefer to do things on my phone on landscape view, but that's hard to do when you're moving around or driving. So, that's why my main homescreen's portrait mode is designed to give my right thumb easy access to the important apps/buttons first, such as phone, text, camera and maps. Music and search are just for convenience. Calendar, browser, address book and e-mail are just for when I have time to stop and reference something for a moment.
Landscape mode will be more friendly to the calendar, browser, address book and e-mail apps, but the other apps/buttons will also be available and within range of my right thumb.
The homescreens that follow after that are broken down by category, such as productivity (business), social/news, etc.