Hhahahah, have been to Mt. Horeb-le. Just awful.
HAve been to Starved Rock a couple times, last time in middle of winter to see all the bald eagles. Terrific.
Mt. Horeb has 4 shops I like to frequent, so it can be done in about an hour. Not worth a trip in itself, but we usually stop on the way home from Chetek, WI.
Only place around Muscatine I'd recommend for a trip for outdoor recreation would be Wildcat Den State Park:
http://www.iowadnr.gov/parks/state_park_list/wildcat_den.html
Do you go to Chetek often? I know a guy who has a home on a lake, goes every weekend over there.