Here are some videos showing the development of PlugIns in Brazil, especially on the city of Recife. We use WMS and PostGIS. This application was called MUL-Mapa Urbano Livre (Free Urban Map) and we used only free software to develop it. Regards to EMPREL
How to see it:
Click on the respective image and then (after reading the discription) click on the link Link to full size image and unpack it on a folder and run the html file on a Browser (I reccomend Mozilla Firefox
).
Search by Neighborhood 
Search by Neighborhood and Block
Search by Street 
Search by Economic Activity set/lot 
Search by set/lot Code and Sequential 
Search by Reg Expressions and Address 
Search by Property Owner (parcel) 
List Owners on set/lot Properties 