Interesting plant. Do you have sandy soil? I did a little research, it seems to like that looser soil. And the article I read also suggested that you eat it!
It is in the mint family, and apparently is crowded out by healthy turf, so if you use the usual organic approach for turf (dry molasses, corn gluten meal, the usual amendments, if needed) you'll see less of it. The article started into the various noxious chemical treatments so I'm not going to link to it, in case someone took that approach as an endorsement.
So where are you? How large is your lawn? Is it into gardens as well, and is it wide-spread or just starting out in a portion of the yard (i.e., did it come through from a neighbor's yard or did it just turn up one day?)