Google Maps
I use it to:
- Locate me.
- Search places.
- Bookmark places.
- Find routes.
- Navigate.



Unique features:
- Built in iPhone.
- Street view (coming to Europe, one country at a time).
- navigation system.
Google Earth
I use it to:
- locate me.
- search places.
- do 3D earth exploration.
- browse nearby Wikipedia and Panoramio entries.



Unique features:
- 3D flight mode.
- Gyroscope sensor view tilting.
- Wikipedia and public Panoramio layers.
Firefone
I use it to:
- Update my location on fireeagle.

Unique features:
- location brokering service. "Update once, update many" feature.
Here I Am
I use it to:
- Mail my location.
- Keep a mail record of my tracks.


Unique features:
- Sends an email with my textual gps coordinates from the touch of a button.
Wizi
I use it to:
- Locate me.
- Bookmark places (private).
- Add friends (private).
- Share my location (mail, friend, friends or public).
- Locate friends.
- Send direct messages. Reply.
- Navigate (to places and to friends).
- Journaling (Picture, text. Private and friends-only).



Unique features:
- Know how distant I am from my friends and from my places by looking at the timetag.
Wizi tries to do everything: Social networking, instant messaging, journaling, navigation. This approach can be risky though, as other more specialized tools may out-perform it. It started as a navigational tool to reach friends by leveraging on user-provided tracking data. This is still, by far, it's greatest asset. A distinctive approach would be to add value to my iphone/gmail contacts, by providing my current location to my contacts and by providing the current location of my contacts. This is what I'm really excited about Wizi. But the Wizi team has to slowly adjust and fine tune their service as they need to compete with traditional navigation systems and typical conversational journaling services. If they want to compete with Brightkite and Loopt, they also need to refine their conversational canvas so users can engage more. So far the Wizi client still isn't released on the App store, and I only got access to it as private beta tester. But you can download it on many other platforms such as windows mobile and blackberry. An Android version is also being developped.
Brightkite
I use it to:
- Locate me.
- Bookmark places (private, friends-only, public).
- Add friends (private, friends-only, public).
- Locate friends.
- Share my location (private, friends-only, public).
- Conversational journaling (text, picture. Private, friends-only, public).



Unique features:
- Best UX for a micro-blogging/journaling platform.
Brightkite does one thing and does it well: it's a location based micro-blogging/journaling platform with a clean interface and a good user experience. It provides a conversational canvas to engage with the community. It's biggest threat is the fact that it doesn't works two-way on the importing/exporting of data. Neither with location, neither with pictures, neither with micro-posts. Thus, I'd rather send a tweet with a link to a picture to engage conversation, than make a brightkite journal entry. However, it does provides an RSS feed for the journal so you can still pipe it to Twitter, to Facebook or to Friendfeed.
Loopt
The problem with Loopt is that it isn't available out of the US (and perhaps Canada). So I really can't go in depth with it. For all I know, it's very similar to Brightkite and, thus, it's based on the journaling concept. However it integrates with Facebook quite nicely (two-way) and it also integrates with Twitter while providing an RSS feed. These features alone make Loopt more "data-portable" than Brightkite. This is very interesting, as my main social-networks are Facebook, Twitter and Gmail contacts (so it's 2 out of 3 ducks).



Unique features:
- Facebook and Twitter integration
- U.S (& Canada?) only.
Plazes
Plazes isn't available yet for the iPhone, though an iPhone app is rumored to be underway anytime soon. The interesting thing about Plazes is that, beyond conversational journaling, it also adds a whole new social object: the conversational agenda. It's basically an agenda/calendar where you share/appoint events. The events that you actually attend get lit up, and you and your friends can always comment on them. It potentiates an integration with your calendaring tool.
Concluding remarks
So I just went through the list of location-based apps I use the most on my iPhone. We must retain that the basic social features are locating, routing, navigating, sharing location, locating friends and journaling. Each of these features have several degrees of security -private, friends-only, public-; and several radius of proximity -exact location, neighbourhood, city-. Plazes goes a step further by adding the events agending feature.
I feel most of these applications are still transient, and I still have this need to import/export my tracks data. I really think those services should work more tightly with fireeagle. Brighkite does update fireeagle, but that's it. There are also other location baseds services like Zintin and Cence me. So please let me know if you're interested to learn more about those. But I'm curious, what location-based social apps do you use?