For Michigan Ski Conditions you can't beat the Weather Underground from the University of Michigan. This is the best chart of Michigan resorts on the Web. Also from the Weather Underground is a list of snowfall depths from around the state. This is not really a cross country trail report, but it does show where the snow is.
Go Ski Michigan has a great interactive ski conditions map for all the Michigan resorts.
OnTheSnow is one of the best. They also feature an Ski-Mail service that e-mails you customized ski reports.
Ski Conditions & Weather are brought to you by Garland Resort. The current weather at Garland Resort is...