Alternate jack points. This link shows one approach, involving the use of a modified ice hockey puck:
http://boxsters.addr.com/jacking.htm
Lots of people have had good luck with that technique. I had some left over lengths of 4x4 (used for fence posts) and like working with wood, so did a variant:
http://986forum.com/forums/showthread.php?t=22250&highlight=jack+stand
It has worked well for me. The most bothersome part (and it's not really all that bothersome) is that I have to drive onto short pieces of 2x10 to elevate the car a little so I can get the jack + the piece of 4x4 under the jack point. I like having them around anyway, and now have 4 of them---I drive the car up onto the four when I'm doing a detailing (or even just washing it). That little bit of additional height makes it easier to work on the lower parts of the exterior.
As I said in my thread, I first jack up at the rear on one side, place the jack stand on the actual jack point, then move to the opposite rear and repeat. Then I do the fronts in a similar manner.
BTW, why can't you use your ramps for the oil change? I do it all the time.