Google Adsense seems to be very sensitive to certain content. I have only posted two entries about Flying Spaghetti Monsterism (this one and this one), and currently the main page displays these two posts among various others about topics such as iPod, podcasting, Ruby, Java, Cafepress, Spreadshirt, Xbox, etc. Still, as of the time of this writing the Google banner exclusively contains ads for websites on religion or spaghetti recipes.
I shudder to think that I might actually be inadvertently promoting religion via the ads displayed on my blog. ;) Those spaghetti recipes might come in handy, though.