Small Engines (Lawn Mowers, etc.): B&S lawnmower spewing oil, self propelled lawnmower, filter area

Question
2 weeks ago I changed the oil and replaced the blade & air filter on my 12 year old Craftsman self-propelled lawnmower. I noticed a leak last week, but it seemed to stop after 15 mins or so. When I pulled the machine out last night, I saw a large puddle of oil below it. I started to mow, and when the engine was running, oil dripped out onto the desk and was dripping below the deck as well. The leak(s) are in the same area, on the rear, right hand side of the engine. Did I just overfill it, or is there a gasket leaking? The dipstick says the oil level is now at the "add" mark.  

Answer
when you check the oil level make sure the dipstick is seated all the way down. If its a screw on type make sure you screw it all the way down to check the oil level. This can make a half inch of difference in where the oil marks the dipstick. If the oil is coming from the filter area you most liely overfilled it or possibly you tipped it on its side carb side down when changing the blade it is possible that the sump gasket is leaking but check out the first scenario first.