There's been no official announcement from the Cubs, but this tweet indicates the team has signed lefthanded relief pitcher Wesley Wright, who was non-tendered by the Rays on Monday:
Can confirm tweet by @BNightengale that Cubs signed LHP Wesley Wright. 3.69 ERA in 70 games with Houston and TB in 2013.— Mark Gonzales (@MDGonzales) December 5, 2013
You're probably familiar with Wright, as he spent five and a half seasons with the Houston Astros, most of those while Houston was a member of the National League Central. He has 25 career appearances against the Cubs, and overall, Wright has been a pretty consistent lefthanded reliever who is used almost exclusively as a LOOGY (Lefthanded One-Out Guy, in case you don't know the acronym).
Wright actually pitched pretty well for the Rays after they acquired him from Houston on waivers last August 12 -- 12⅓ innings in 16 appearances, with a 2.92 ERA and 0.973 WHIP.
The Cubs haven't really had an effective LOOGY in quite some time. Recent managers have used James Russell that way, but he's not really a LOOGY. For his career, he has held lefthanded hitters to a .231/.313/.342 mark, with just seven home runs in 506 plate appearances.
The move leaves the Cubs' 40-man roster at 38. No, this isn't a big move either. But it could be a useful one.