There are a few guys i would keep an eye on, but just don't do anything crazy and dump someone you might need.
Given a full season, i think austin kearns can produce. Last year he had 24 hr, 86 rbi. granted, the nationals offense isnt that great, but if he has a breakout year he could top 30 hrs fairly easily.
just another few guys i would keep an eye on:
Ryan church, ryan garko, garret anderson.
at shortstop Jhonny Peralta was somewhat of a letdown lastyear, but don't count him out to rebound to his 2005 numbers, which were .292 average, 24 hrs, and 78 rbis, which are acceptable for a shortstop, although jimmy rollins is no slouch either, but a hot peralta would certainly be good trade bait.
keep an eye on some of the younger guys coming up, especially in june and july, when a lot of the struggling players tend to get replaced.