The NYTimes is running this story which seems to indicate that there is very significant interest in signing Brian Giles to play centerfield, i.e., Joe Torre has been asked and has called him.
Giles has enviable stats starting with +.400 OBP and many more walks than whiffs. He boasts decent speed, an above-average arm, decent pop and by all accounts is a good citizen. On the downside he's going to be expensive and will be 35 by opening day.
Another name being bandied about is Juan Pierre who trails Giles substantially in every category EXCEPT stolen bases. He is however, 28 and might be one of the fastest players in the league. Apparently though the Yanks have soured a bit on him.
Johnny Damon is a cut beneath Giles offensively but has better range in the field but a below average arm. He's four years younger though but will be more expensive.
The safe bet is probably to go after Giles as Damon will lose some offensive punch out of Fenway (he's 40 points lower on BA and 50 points lower obp from 2002-2004).
There's plenty decent pop in the lineup though but the Yanks could do with a chaos creator on offense and stellar defender that they haven't had since Bernie in his prime. Juan Pierre would be cheaper and would run down flyballs in the gaps better than any of the other candidates. His presence would also protect Matsui (above-average) and Sheffield (average) in the corner outfield. I'm tempted to take Pierre in a decent deal over Giles as he would seriously upgrade the defense and the type of catalyst one would want in the playoffs.