Buster Olney tweets that a claim was awarded on Carlos Pena. Depending on when that actually happened, the Cubs and the mystery team at the moment have about 48 hours to work out a deal. If nothing can be hammered out, the Cubs can pull Pena back off waivers or they can just let him go to the team and save the remaining salary left on his contract which includes the $5M deferred money he's owed on January 1st, 2012.
While Pena is now on track to be a Type B free agent and there's certainly plenty of value in the possibility of getting a supplemental round pick for him (although no sure thing), there's probably more value at the moment in saving the $5.5M or so he's owed, regardless of the prospects they may get back.
Possible Correction: It seems there's a bit of a confusion that if Pena is just given away, the Cubs could still be on the hook for the $5M in deferred money. Not sure why it works that way or how, but that's the current rumor by MLB Trade Rumors and Arizona Phil.
Update: Rosenthal tweets:
Pena claimed, but #Cubs likely to pull him back. Need 1B for 2012, want to keep options open. Did not get good offers before 7/31.
Considering Hendry's claim that he didn't want to make too many deals before the deadline, hopefully the thinking has changed.
Update #2 from Rosenthal:
This has gotten about 90% less exciting than it was an hour ago. My math tells me then that the claiming team would be on the hook for about $1.67M if the Cubs just let him go.
Update #3 from Jon Heyman says it was the Yankees. I assume they're just happy to take on the money then.