To auto-post to Facebook from Google+:
1. Login to Facebook.
2. Go to http://facebook.com/mobile
3. Copy your unique e-mail adress (it'll say "Upload via Email")
4. Go to Circles on Google+
5. Add the Facebook email address to a circle (old or new). Name the email address
something like "Facebook" or "Post to Facebook".
6. When you want to post to Facebook just include the individual Facebook user you created in step 5 (not just the circle).
By specifying that individual email explicitly, you don't have to check "Also email..." to have it sent via email to Facebook; this means you don't have to spam email a bunch of other people you might have in your circles that are not users yet.