Tyler/Xander,
I've not personally used iterate much but I have long realized this tool could be very useful. If you'll permit me, I'd like to re-state what the overall purpose of both iterate models is to ensure I'm understanding them properly. Please chime in to correct me in my attempts to understand these great and varied examples.
In Xander's example, this model creates a single feature class for each unique name from the input feature class called "Selected Feature Class". I can see this ability to be very useful, especially using the name (%Value%) of the selected field for the output FC name.
In Tyler's example, (if I'm understanding it correctly) the purpose is to export a summary *.CSV of do some calculations on several values. That model iterates on the Name field of the input "Markets_Merged" feature class and literates a selection based upon that resultant value. Next, that model performs a spatial selection on "Newpatients_112015" (a point feature class, I'm assuming) that are within the selected market name. When the resulting new patients are selected that are within the iterated market name, the market name (%Value% from the iterate function) is calculated to the newly added "Market" field name on the new patients feature class. Lastly in Tyler's model, summary statistics are run to create a CSV table with a count of the site and market fields (presumably of a count of new patients per site and per market) with the iterated market name in the file output CSV title.
Thank you both for this opportunity to learn more about iterate functions!