I've never advertised my blog because I'm very new at it.
I do however have a website that I started 12 or 13 years ago and it ranks in top 5-6 (#1 for years, but now with all the blogs, my ranking has slipped to 5 or 6) google searches under "single mothers". I've never advertised it either, but have ocassionally paid pr firms for a press release. And each time it was very effective.
Another thing I have done is try to time my press releases with relevant current events. Mothers Day, the media's always looking for stories about moms and I've got a lot of them. Then around Christmas, they're interested in our Angels Assistance Program and the tangible help we provide moms around the holiday.