Tekumse, in the comments for the post below, pointed out that there's an update at the MER website confirming the beep this morning.
SPIRIT UPDATE: - Jan 22, 2004, 10:35 am PST
The Mars Exploration Rover Spirit radioed a beep Thursday morning confirming that it had received a transmission from Earth. Still, it has not returned any data since early Wednesday. Flight-team engineers for NASA's Mars Exploration Rover Project are working to diagnose the cause of communications difficulties.
The confirmation is good news. I've got my fingers crossed, and hope it's some minor software fault that can be corrected or routed around.
While you're at the MER site, do check out the nice interactive Flash animation (load it from the MER site to get the correctly sized window).
update: I've read through the comments at /. (so you don't have to) and the only informative posts were a post by mlyle which points out the varios subsystems assumed to be functioning, and post by goon which points to some good background information.
