I found this search tool for running events around Chicago..

For Chicago specifically, here are lists of events for the next two months.

Listings for April:

Running Network Calendar System link

Apr-05-08 Chicago Lakefront 50K George Cheung Memorial Race Chicago IL
Apr-06-08 Run for the Cheetah 5K Chicago IL
Apr-13-08 Race to Wrigley 5K Run Chicago IL
Apr-26-08 Path to Progress Chicago IL
Apr-27-08 Universal Sole Lakefront 10 Chicago IL
Apr-27-08 Ravenswood Run Chicago IL

Listings for May:

Running Network Calendar System link

May-01-08 Race for a Safe State: A 5K Run, Walk and Roll Chicago IL
May-03-08 Run To Remember Chicago IL
May-04-08 Chicago Distance Classic Half Marathon Training Program Chicago IL
May-04-08 C4 Miles: Making Strides for Mental Health Chicago IL
May-05-08 Polish Constitution Day Hash Chicago IL
May-06-08 Interval Track Workouts for Women Chicago IL
May-11-08 Y-ME's Race to Empower Chicago IL
May-18-08 Heartland Spring Chase Chicago IL
May-18-08 Alternate Route 8K Race Chicago IL
May-22-08 JP Morgan Chase Corporate Challenge Chicago IL
May-24-08 Fleet Feet Sports Soldier Field 10 Mile presented by adidas Chicago IL
May-25-08 Chicago Hash Memorial Day Hash Chicago IL
May-26-08 Ridge Run Chicago IL

I'm signed up for this Saturday's Path to Progress 5k at Montrose Harbor.

Here are the events for June:

Running Network Calendar System

Jun-01-08 Run for the Zoo Chicago IL
Jun-05-08 Advanced Speed Training for Endurance Runners Chicago IL
Jun-06-08 Madison-Chicago 200 Relay Madison/Chicago IL
Jun-07-08 Takeda WonderGirl 5K Chicago IL
Jun-08-08 San Juan 8K Chicago IL
Jun-19-08 UCTC Summer Meet - 1 Chicago IL
Jun-19-08 ABC7 Jim Gibbons 5K Run, 3K Walk & Survivors' Strut Chicago IL
Jun-22-08 She's Got Sole 8K Chicago IL
Jun-22-08 Lakeshore Athletic Clubs' Walter Kaiser 5K Run/Walk Chicago IL
Jun-26-08 UCTC Summer Meet - 2 Chicago IL
Jun-28-08 Proud To Run Chicago IL
Jun-29-08 Race to Taste Chicago IL

While maybe not a true running event, I did notice Bark in the Park 2008 is not listed for May.

BarkInThePark.org
The Anti-Cruelty Society's
14th Annual Walk for the Animals
Saturday, May 3, 2008, 9:00 a.m.

More details:
Bark in the Park - Home Page

This was just announced today:

Nike+ Human Race: The World's Largest One Day Running Event -- 1 Day, 1 Million Runners, 25 Cities, 25 Top Musical Acts Join in Unprecedented New Race Experience

"Nike today announced the Nike+ Human Race, the world’s biggest one day running event ever, offering runners across the globe the chance to compete together on August 31, 2008. The 10k event will span multiple continents and cover 25 cities, including LA, New York, London, Madrid, Paris, Istanbul, Melbourne, Shanghai, São Paulo and Vancouver. Following races in each city, participants will be treated to an exclusive music concert featuring one of today’s top artists."



Official Nike+ site:
http://www.nikeplus.com/

The weather should be good for this... I'm going to do the 5k. I don't think I've actually done any running or been on a treadmill for almost 2 mos.! But I did full a full 10k in August (The Human Race, see above). So I hope I can jog slowly the full three point one miles.

Hot Chocolate 15K/5K

Here's a much better listing of local running events: Chicago Athlete magazine event calendar

I like the RN Calendar --

Running Network Calendar System

Here are the running events for December

Running Dec-07-08 Chicago Jingle Bell Run/Walk Chicago IL
Running Dec-14-08 Rudolph Ramble 8K Chicago IL
Running Dec-28-08 Universal Sole Resolution Run Chicago IL
Running Dec-31-08 Last Race of the Year Chicago IL