We were just able to book our wedding for Nov 5, 2010. I plan on sending out our STD's at the end of February. I think that 8 months 'formal' notice is enough for our guests, and most are already aware of the wedding location. Since we were JUST able to actually book our wedding date, sending them out earlier than this was just impossible for us.
Formal invites will be sent out at the end of March, or as soon as I'm able to get them all put together since I'm taking the DIY route.