The following crime data reports (.pdf format) are available publicly, courtesy of the Chicago Police Department:

Annual Reports from 1996 - 2005
Crime Trend Reports

• Murders: Domestic Violence, & Child Abuse, with 10-year comparison
• Reported Robbery Incidents from 1999 - 2005

Domestic Violence Reports from 2004 - 2006 (Quarterly Statistical Reports)
Hate Crime Reports from 1996 - 2005
Homicide Reports from 1999 - 2005
Juvenile Reports

• Juvenile Arrest Data from 1999 - 2005
• Murder of Persons Under 20 Years of Age from 1991 - 2004
• Gang Motivated Murders from 1991 - 2004

Index Crime Statistics from 1999 - 2007 - view year-to-date statistical data on crime in Chicago (either citywide or by district comparison) via their Crime Summary Report which is produced by the Research and Development Division of the Chicago Police Department
Index Crime represents serious crimes broken down between violent crimes (homicide, criminal sexual assault, robbery, aggravated assault/battery) and property crimes (burglary, theft, motor vehicle theft, arson).

Statistical & Crime Data Request Form - link to .pdf request form for data on Chicago from the Chicago Police Department.

Chicago Police Department's Clear Geographic Information System