OpenGuides is a complete web application for managing a collaboratively written guide to a city or town.
This means that it's software which acts something like a content management system. It takes the pain and technical know how out of creating a city guide, and makes it easy for people to work together to produce and update information. This means that your city guide has a good chance of being up-to-date, informative, unbiased and useful. The more useful it is, the more people will potentially contribute. It's a snowball effect.
Because it was written to be city guide software, it has some impressive features such as searching for things by area, or within a certain distance of other places. You don't need to do anything special for this, just provide your Guide with the data and the software will do the work for you. You can even integrate your Guide with mapping sites such as Google Maps, and image hosting sites, with the mininum of effort.
Because it was written by a bunch of geeks, OpenGuides has some groovy behind-the-scenes features, mostly involving heavy use of RSS and Atom Feeds, the Resource Description Framework (RDF), and MicroFormats. This means that other websites and software can pull information from your Guide, display it in different formats, and play around with it in different ways, all with the minimum of hassle. Again, you don't have to do anything special for this; it Just Works.
For a good, if technical, introduction to the concept behind OpenGuides, read OpenGuides on perl.com. Feel free to visit the OpenGuides homepage and look around, explore the OpenGuides linked to from there.
Wiki, bug-tracker and source repository: http://dev.openguides.org/