Always be training!
Most of these sites are for youth baseball as there are very few baseball coaching sites for adults. No matter - we all act like a bunch of 5yr olds anyway.
Baseball Drills
More Baseball Drills
Practice Procedures - Making it fun
Even more drills
Proper Execution of a Rundown. This is targeted to softball players, but the fundamentals are the same.
Ever wonder where Josh, Brian and Jay get all the practice drills? click here
CrossFit - One wicked workout for those who dare. click here