Granted, it's an unusual, potentially unreliable source. Walterfootball.com is known for its offseason commentary, particularly the draft and, more recently, free agency. The site doesn't do a ton of reporting, but from what I can recall, it's been pretty accurate in the past with respect to its "sources." It is, however, a small sample size, so take this with a grain of salt.
At any rate, writer Charlie Campbell says in the linked post that a source has told the site that the Bengals plan on using up most of that $55 million it has in salary cap space. Campbell goes on to speculate (as many of us have) that much of the spending will be used on retaining 2013 and 2014 free agents, such as Geno Atkins, Michael Johnson, Andre Smith, and Carlos Dunlap.
More speculation on his part centered around the running back and safety positions. The safety free agent market is relatively deep compared to other years (although so is the draft, so we'll see). In addition, RB Reggie Bush will be a free agent this spring, and he fits Gruden's desire for a game-breaking running back. Personally, I'd like to see them pick up a rookie for that role, even if he's paired with Bush. Bush has a history of injuries, and he's not getting any younger.