We've found a couple of websites that have been very useful in the charting/planning stages of our Lake Michigan cruise.
1) OpenCPN - Awesome free software to convert your laptop into a GPS chartplotter.
2) NOAA Nautical Charts - Great for desktop cruising, planning and some printing.
3) NOAA BookletCharts for the Great Lakes - Excellent for printing your own charts in 8.5" x 11" booklet format.
4) Lake Michigan Waypoints - Perfect for updating your GPS with common waypoints while at home.
5) Distances Between Lake Michigan Ports - Nice, quick tool from gosail.com