Of course it's only OPS, and it's just from July 21st of last year until yesterday, but here are the top thirty hitters in baseball over that time span:
Looks like Justin Upton has hit as many homers in the first 3+ weeks of April as he did over the last portion of 2012. And Carlos Santana may at last be rounding into form in what is now his age-27 season (though he can really hit into those DPs, can't he?).
Note the presence of both Bryce Harper and Mike Trout on this list. Highest BA: Torii Hunter (.366). Lowest BA: Mark Reynolds (.244).
Data courtesy of David Pinto's terrific Day-by-Day Database.