Nick,
Freedive-a-Palooza happened back in July. We'll have another one next July so just email me and I 'll keep you posted.
Greg, You can freedive Lake Geneva, but you need a boat, and a flag, and they love to give out tickets for any infraction. It is a very nice, and somewhat deep, lake with really clear water- for this part of the state. The only downside is the boat traffic. Going this time of year would be the best bet since it calms down after summer ends.
The best bet for good vis right now is still Lake Wazee, but it's a long drive form illinois. Lake Michigan has some really great vis, but this time of year it's rough almost all the time and the vis goes way down when the waves build up- which is why we get so many surfers out there during the next 6 weeks.

I was talking to my brother-in-law on sunday and he siad it's been rough almost every day for the past month- he's a commercial fisherman out there.
The local lakes by me, in Madison, are starting to improve, but it will still be another month before I start diving them again on a regular basis.
One site you can check for other lakes is Lakesat.org as they have a very good system to check the vis on the lakes in your area.
Racine quarry was really good for a while in the 90's, after some divers dropped bucket full of zebra mussels in there to clean it out. Around 5 years ago it took a turn for the worst and now is bad pretty much all of the time.
You could give a call over to Pearl Lake, but the owner is NOT interested in having freedivers in his lake- which is tyoo bad since it would be the perfect playground. I've had tlaks with him aobut it in the past, and have had other instructors friends of mine go to bat for me, but he's just too closed minded to give it a shot. Maybe if he starts getting lots of calls he might realize that it would help his buisness?
If you have a dive Kayak, or don't mind a LONG swim in very shallow water to get to the good stuff, I would highly reccomend Beaver Lake in Waukeshau County. Very expensive, and hard to get on, lake but super nice for spearfishing and freediving. Not super deep but lots of fish and not a lot of boat traffic- forget about a full sized boat as their "launch" is a flight of stairs to get aorund DNR regualtions.
Hope that helps out a bit.
Jon