I recently acquired an 04 Aveo with a clunking rear end...After doing a visual inspection and some research here I determined that it was likely the rear axle bushing.
As I was poking around the web I found this website:

VWVortex.com - How to: DIY rear axle bushing replacement, MKIV

Seeing as some of the other suspension components were easily adaptable from the VW world, and the striking similar appearance between the VW bushings mentioned in the above how-to, I decided to order a set and see if they fit. Sure enough, they worked perfect. I had to taper the first 3/4" of the bushing to get it to pull straight into the axle, but it is a really tight fit and the clunking rear end is gone.

So if you're going to replace your own rear axle bushings, order VW p/n 1J0501541C and follow the how to above... Cheaper than a new rear axle from GM and cheaper than the bushings from ebay.

Hope this helps everyone save a few pennies. The VW bushings cost me about $50 after shipping.