I realized that I talk a lot about how important ratios like K/9 and K/BB are in predicting future performance, but I've never really presented the evidence for that belief in this blog. Here's a link to a 2004 Article in Futility Infielder that summarizes a lot of the information and provides links to virtually all the important research that had been done on the topic up until then.
In addition, there are two books that devote at least a chapter to the topic and have tons of other great baseball research if you're into this stuff. I've read 'Baseball Between the Numbers' (which is by the staff of Baseball Prospectus) and although I haven't read 'The Book' yet, the authors (Tom Tango and Mitchel Lichtman) have published a lot of great work online, so I'm looking forward to having the time to read it. Don't be fooled by it's current lack of availability...it is completed, and just looks like the hardcover version is out of print so they're taking pre-orders on the paperback.