Oh, yeah---lumber that's in good shape and assembled right (like in Rick's crib) will hold one helluva lot of weight. It's used to build house foundations!
I've for years used ramps made out of 2x8s. (Sorta wish I'd used 2x10s, although as constructed they have the obvious advantage of being lighter.) I've got a sloped driveway, so I back onto them for oil changes. Sometimes (as in this pic) I'll use a couple of my smaller ramps under the front tires to give a little more lift and to help accomplish a level car. (I should add that after this pic was taken I chocked a couple of the wheels before getting underneath the car.)
I've got 4 of those short ramps and use them to lift the car a little to be able to get the jack under it, or even if I'm just detailing the car (wash, wax, whatever)---just so I don't have to stoop quite so low to get the lower portions.
Marck makes a good point. I remember driving up on a separate piece of 2x8 or 2x10 one time (I don't remember why I wasn't using what's in the pic---maybe it was before I made them). But I over-gunned it a little and it fired outta there like it was coming out of a cannon! My dog was running around the yard---I'm super glad he was not behind the car at the time
I think the chunks of wood I have attached to the top level of the ramps helps some, plus (of course) it makes it less likely I'll back all the way off the tall end of the ramp.
