Children In Urban America - An online archive funded by Marquette University and the National Endowment for the Humanities that shows the many ways children experienced city life during the last century and a half.
Milwaukee Public Museum Photo Collection - Collection of images of Milwaukee taken by Sumner W. Matteson. The Museum also offers a research and photo library which may be of use to academics or professional researchers.
Jazz Age Chicago - Obligatory link to Scott Newman's great site about the history of Chicago which provided an influence and model of a useful local history website.
Amateur History Sites:
MSOE Milwaukee Architecture - Dr. Steven Reyer's website and catalogue of many historic Milwaukee buildings.
Links To The Past Geneology Resources - An excellent website with a huge amount of information on Milwaukee's history, most of it related to geneology.