It's a full YEAR before August 2012. I think you should be looking now and applying to jobs that state they want a start date around when you're looking to switch jobs. If there are any particular labs or professors that you really want to work with, sending a letter of inquiry/interest about future positions may be a good idea to do now also (my friend got a job this way). However, most jobs listed right now usually want immediate start or start dates within give/take a month, so launching a full-blown job search right now is pointless.
I think you should start your active job search about 2-3 months before your ideal start date. You'll also have much more to put on your resume because you'll be able to include cool things you're doing at the NIH. Good luck!