I wrote about the advantages of using a pace calculator in a previous post. This is the Jack Daniels Running Calculator and I've been using it to help with my training and goal setting for Boston as well as my recent shorter distance races.
With permission from The Run S.M.A.R.T. Project, I've included this calculator at the bottom of my blog. (This is a screen shot - scroll down to the bottom of my blog to use the actual calculator.)
I encourage you to use this to help set your own goal pace and plan your training accordingly. Reevaluate your goals as your fitness level increases and your race times decrease.