A government rate have been arranged at $83/night for any size room at a 3* hotel in Naperville. It has a nice lounge for working with wireless, nice views, etc. and is 10-15 min from the east gate of Fermilab. You can enter Fermilab at any gate with any photo id. (See also http://www.fnal.gov/pub/about/public_affairs/currentstatus.html)

The address of the hotel:

The Courtyard Chicago Naperville
1155 East Diehl road
Naperville, IL 60563

Directions to Fermilab:
From the hotel turn RIGHT onto E.Diehl Rd.
After N.Washington St. E.Diehl Rd. becomes W.Diehl Rd.
Follow W.Diehl Rd. to Mill St.
Turn RIGHT onto Mill St.
Merge Warrenville Rd.
Turn right onto Batavia Rd.
Follow Batavia Rd. to Fermilab East gate

Reservations can be made directly (use the name Fermilab) at 630-505-0550 or through the general Marriott reservation number, 800-321-2211.

There are slightly cheaper hotels in Aurora on the west side of the lab. Here is a more extended list (lodging rate for Kane County $67 and for DuPage $83):
Comfort Inn - Geneva - Kane
Candlewood Suites - Warrenville - DuPage
Extended Stay - Naperville - DuPage