Since everyone else covered this story (Hank at ecoGeek, zdnet, the hugger) I might as well too, even though I don't have a lot to add.
Dell has a Via-like plant a tree campaign, where you give them up to six dollars when you buy a machine, and they will give it to either the CarbonFund or the Conservation fund. It supposdedly covers carbon emissions from the 'puter over a three year life span. Just like Via. It doesn't cover the carbon emissions from building the thing.
What to make of it; well, it overshadowed Cisco's announcement this week about going green, and IBM's has had a green campaign for a long time. With the desktop going away, Dell's in a tough spot, as J.P. Morgan noted when they downgraded their stock last week. I personally would like to see six year maintenance contracts.
It passes the straight face test. But If you want to bypass Dell, just send the six dollars to me. I'll forward it along.