I am yet to see any ad setup that guarantees they are not visually annoying. Most (reputable) ad networks guarantee they filter ads and remove the evil ones. I haven't seen one that delivered. I do not see how they could - manual review of each ad is not scalable and advertisers would not abide by it, they'd just move to network with less stringent rules.
I believe Project Wonderful is the closest thing I know - it's a manually-reviewed ad network used for webcomics, with the downside that it's accordingly much less valuable for site owners.
