Galena - 2nd or 3rd week of May, longish sprint Galena is a great local race, just 3 hours from Chicago. It's harder than you would expect for a sprint because it's incredibly hilly. It's also a tough race for new triathletes because it has two transition areas so logistics are tricky. The club usually rents houses for the weekend and we have a big party at one of the houses after the race. Great way to kick off the season.
Tri-shark - 1st week of June, sprint Another great local race by a fantastic race director. It's a great venue in the state park, with very flat bike and run. The shark trophies are awesome and the post-race feast is always great.
Evergreen - 2nd week of July, sprint and olympic Organized by the same race director as tri-shark so it's a great local race near tri-shark but in a different park.
Steelhead - first week of August, half ironman A good place to do your first half IM, especially if you have an audience. Beautiful location in St Joseph, Michigan. Unfortunately it's also very expensive (both the entry and the hotels) and the race is very large but well organized.
Chicago Triathlon - last week of August, sprint and olympic Our home race so you can't beat the venue. It's one of the largest races in the world so transition is crowded and you may have a long wait until the start. It's also pricey, but you can save money on a hotel! Hard to beat a home town race on lake shore drive.
Ironman Wisconsin - second week of September, ironman If you want to tackle ironman, do it here. It's a great venue and you'll have lots of club support. Ironman races are very well organized. The catch - you have to plunk down $500+ the year before!