My local city government also recently published a detailed interactive online GIS map of the city, including all lot boundaries, buried utilities, etc. It's great to feel like the public can easily access what is meant to be public record, rather than relying on for-profit third parties to make it available to us.
I really like the ESRI API's (much faster than Socrata). This is a crazy url, but they do allow for different SQL operations (including spatial operations) right in the API. Here is top 10 crime street segments in Raleigh for example:
