Here are a few trail runs that come highly recommended:

Runs:

Holiday Park Trail Run - Trail race in Indianapolis on March 21, 2009

McNaughton Park Trail Runs - 50 mile, 100 mile or 150 mile runs on trails in Pekin, IL on April 10-12, 2009

Zionsville Anti-Mini Run - 3.1, 6.2, 9.3, 13.1 mile trail runs in Zionsville, IN on May 2, 2009

Dances with Dirt - Individual 50 mile or 50K (or 100K relay team) trail run in Gnawbone, IN on May 9, 2009.

Run with the Foxes - 13.1 mile trail run benefiting the Hoosier Hikers Council run in Morgan Monroe State Forrest (near Martinsville, IN) in May.  Check the website for the date.

Knobstone Trail Mini-Marathon - 13.1 mile trail run also benefiting the Hoosier Hikers Council run in Morgan Monroe State Forrest (near Martinsville, IN) in October.  Check website for date.

Outback Scramble - Wacky 5 mile cross-country run where you make your own trail on the west side of Eagle Creek Reservoir in Indianapolis.

Series:

Kennekuk Trail Runners Events - Whole series of trail running events put on by the Kennekuk Running Club near Danville, IL.  Great events include the Howl at the Moon 8 hour run in August.