There are a lot of questions the front office will need to address this off-season, not just in terms of "Which holes are there to fill?", but also in terms of "Are there holes to fill at first base and catcher?" The first base question may be a bit easier to answer, because while Justin Morneau is hopefully the primary option there's also Joe Mauer, Chris Parmelee, Luke Hughes, and, potentially, Michael Cuddyer available to fill in.
The potential hole at catcher will be a bigger question mark, in the scenario that Joe Mauer's position shift is closer to happening than we'd like to think. By this point it's pretty well established that it's a matter of when, not if, Mauer will make the change. If he needs to begin the transition next season, the Twins will need a catcher who can aid in that transition by catching more often than a typical backup. Not just that, but make a positive contribution on the field in terms of runs and wins.
There are no good in-house options currently. Trades are fun to speculate over, but the best and easiest short-term answer may lie in free agency.
Below is a list of upcoming free agent catchers. I've excluded players with options (Ryan Doumit, Yadier Molina, Kelly Shoppach, Chris Snyder), catchers who haven't played in 2011 (Jason Kendall), and guys who appeared in less than 30 games (Ramon Castro, Josh Bard). Based on what you see here, and what you know, if the Twins were to target a free agent catcher who would you prefer?