The explosion of apps for the iPhone (and iPod Touch) includes plenty of tools to help you navigate city streets, engage with your community, and enjoy public spaces as never before.  Below, a roundup of some of the best Placemaking-friendly apps:

* Markets and eating local. Locavore ($3.99) uses the iPhone's GPS capability to find your closest farmers' markets, and tells you what's currently in season near you, from almonds to zucchini.  It also links to recipes and information for all 234 food varieties it tracks -- very convenient when you're trying to figure out what to do with quince or sapote.  Farm Fresh NYC ($2.99) works similarly for the Big Apple, and includes a graphical grocery list; San Franciscans can use Sprout (free) to track down markets, CSAs, and other local food sources.  (And check out this group that combined their love of Apples with their love of (locally-grown) apples!)

* Public transportation, walking, and cycling. The iPhone's standard Maps app (via Google) allows you to specify walking or public transit (over 400 cities' systems are covered) when seeking directions.  This group is pushing Google to include bike directions as well.  This cool, soon-to-be-released "augmented reality" station finder overlays subway directions atop a real-world view of your surroundings.EveryTrail (free) tracks your bike route and geotags photos you take along the way.  And Bike Your Drive (free) tracks your ride, and displays stats about how much money and carbon you've saved by biking instead of driving.

UpNext 3D NYC ($2.99) changes the experience of walking in New York.  Its fancy yet functional 3D map lets you fly over and zoom in on specific buildings -- tapping a train station displays an underground map of NYC's subways, and tapping a building tells you what businesses are located there.  You can tag the map with notes about your favorite places, view the most popular or just-opened spots, and even locate the closest bike rack.  While you're out and about, use a free crowdsourced toilet-finder app, like SitOrSquat, to find public (or public-friendly) restrooms.And for those who absolutely can't tear themselves away, Email 'n Walk (99 cents) displays a video feed of the outside world via your iPhone's camera, while you continue typing away in a transparent window... use with care.* Parks. A search for "parks" in the Maps app tags public parks in your area, though not always perfectly.  Off Leash (free) hosts a growing database of dog parks near you.  For parents, The Hidden Park ($6.99) is an ingenious app that creates a living video game in the park, encouraging fitness and educating kids about the environment.  Currently released for ten parks worldwide (including NYC's Central Park, Toronto's High Park, and Sydney's Royal Botanic Gardens) with more to come, The Hidden Park takes kids on a park-wide scavenger hunt, in which they solve puzzles and photograph landmarks in order to reveal magical creatures and save the park from developers.

* Building great communities and engaged cities.The iPhone makes it easy to stay on top of community happenings.  Everyblock's free app compiles neighborhood news within fifteen US cities, including crime reports, business licenses, and media mentions of your block; outside.in's web-based Neighborhood News (free) aggregates hyperlocal info from blogs, event listings, and even Twitter tweets.DoGood (free) aims to "unite individual acts of kindness into a significant movement."  Each day it suggests a simple good deed you can do in your community.  Check it off and add a note once you've done it; DoGood tracks this info from the worldwide community of DoGooders, so you can see the collective impact of all these random acts.Local governments are also jumping on the iPhone bandwagon.  San Francisco's free EcoFinder shares local info on how to recycle different materials, and Boston's Citizen Connect (soon to be released) lets citizens submit photos of potholes and graffiti straight to City Hall.Apps for Democracy is a great example of the wisdom of crowds.  Last year, the city of Washington, DC partnered with a web developer to sponsor a contest to make DC's abundant public data useful to citizens.  The effort yielded 47 iPhone, Facebook, and web apps that use the data in a variety of creative ways -- from a carpool matchmaker to Stumble Safely, which integrates transit maps, crime data, and liquor license info to get you home safely after a night out.* Telling your own story in public space. Mobile technology can also help make public space "yours" by allowing you to record your experiences in a place.  MobileMapMe is a free web-based app that allows you to create your own maps of places and share favorite spots with friends.  Whrrl (also free) lets you tell "stories" by integrating photos, text, and location information into a narrative you can share on Facebook or Twitter.What other apps have helped you engage with public space in your community?  What tools would you like to see?  Earlier this year, PPS hosted a DIYCity workshop of programmers and urbanists exploring how new Smart Phone applications and other emerging technologies can be harnessed to support better cities.  The results of the meeting were posted on a wiki that can be added to.PPS plans to develop an online version of our place audit that will allow people to rank and evaluate public spaces and search for and compare spaces.  We are open to any ideas and help in further developing the idea and the application.