We regularlyreceive requests for information on precipitation (especially rainfall) for class assignments. Thelinks below should help considerably with this sort of data. There aresome additionallinks under the "historical data" tab.
This site, run by the Midwest Regional Climate Center at the University of Illinois but by no means limited in scope to the Midwest, requires users to register an account, but it's free to use. This is, by far, the most user-friendly tool for searching and accessing weather station data, going back to the 1800s for the older stations. It might not always be the best place to get large data sets, but especially for the layperson just looking for their town's weather on a given date, this is my preferred resource.