Well, it turns out that NASA wasn't spamming me exactly. I was receiving the emails through the Slacker Astronomy notification system. People are invited to make comments and suggestions for topics through the Slacker website. Someone at the Office of Public Affairs at Goddard Space Flight Center decided to add the Slacker email address to the list of news services and blogs they send these press releases to. Doing this without asking if we wanted these notifications is essentially spamming, but the lady at Goddard was very apologetic and reasonable, and we have been removed from the list.
Hey, they're NASA. We love NASA. Stuff happens.
Although I'm sure my complaining has put me on yet another government watch list and blown whatever chance I had at going into space...ever.