Information Systems:
This is going to be about management, policies, procedures, infrastructure, and a lot of administration stuff. You'll probably cover some basic programming and database, as well as networking concepts. May touch on security concepts as well. Target job will be Project Manager, or SAN Specialist.
Information Technology:
This is going to be a lot more technical - it's going to be about setting up routers and switches, voice systems / voip, linux, some programming, running ethernet, etc. This has a lot of cross referencing with IS. Target job will be Cisco Engineer or Unix Specialist.
E-Commerce:
This is going to be a lot of programming, database, web and graphic design, marketing, and sales stuff. Target job will be Java/.Net Developer, or Data Warehousing.
Every college seems to do it a little different, and those target jobs are just minimal examples. What interests you the most about IT?