I do my own oil/filter changes on all my vehicles (with eight cars and three bikes, it adds up!) and the lawnmower/rototiller/shredder/etc. used oil goes into the same jugs that the other stuff goes, and then it all goes to the local auto parts store (Kragen/O'Reilly). No, not all the cars are running - right now I'm doing regular oil changes only on four of them, and some are driven so infrequently I've extended the oil changes (in time, not mileage). More than enough, though!
I don't know why they don't make lawnmower oil changes easier. On my old mower I had to put the thing on bricks to get a pan under it to drain the oil. On my new mower I think I actually have to tilt the thing to drain it out the filler. Oh well. I usually change the oil every spring. This mower has an easy life: the only lawn here is the small one in front - about 30' x 30' max. And it has a magnolia tree and three rose bushes in it. So not a lot of grass to actually mow.