Essentially I want to be able to see an annotation on my charts so that I can say "After we sent the EBlast, X happened to Y" (where Y are pageviews, visits, whatever). Is there a way to do _gaq.push('[_createAnnotation]') or something?
There is currently no way to programmatically create new Google Analytics Annotations.
There's an open issue on the Google Analytics issue tracker asking that it be made available. It's been starred by 262 people; you can star it to signify that you'd like to see it implemented.