nifty little online tool that will create a custom marathon wristband for you. If you enter your desired finish time, it will have splits calculated out for every mile of the marathon for you printed on the wristband. Of course, every 3 - 4 miles is highlighted in yellow as a good time to "eat a Clif Shot or 3 Clif Bloks" but whether you enjoy Clif products or not (I happen to, their Mocha gels are my go-to race gel), it's a good visual reminder to keep on your nutrition schedule.
You could easily use this to pace an Ironman marathon or a half-mary or half-IM as well.
The Ironmom Extra Mile: Here's a nice short-n-sweet article on marathon pacing by a 25-time marathon finisher:
And here's a great downloadable PDF of Marathon Racing Strategies by the same author, Mike Stapenhurst.