HipGeo is a free app that can create a sort of travel blog on the fly with as much or as little user input as you like.
It tracks your location, allows you to add comments and photos, and can even playback an animated map of your travels.
You can keep your travel info to yourself as sort of a diary, or share your adventures via Facebook, Twitter or email. Alternatively, publish your info to the world through a web page or using the app itself.
HipGeo also shows posts from people nearby who've elected to make their locations public. I didn't see a lot of activity near me, but I did see some public posts from the bigger nearby cities, and a lot of activity at the Consumer Electronics Show in Las Vegas.
The app works well, and gives you granular control of your privacy ranging from 'keep my travels to myself' or 'let the whole world know where I am and what I am doing.' The app has some safeguards to protect your battery life, because it runs in the background when you activate it. One setting (places) saves your battery by only uploading a new location, while another setting (places and routes) tracks you from moment to moment. It's better to use the latter setting selectively or only if you're plugged in.
HipGeo is an interesting take on location broadcasting, blogging, navigation and social integration. It seems to work as advertised, and is a really effortless way to create a blog of a vacation, or even your daily activities. I think users should take care about publishing photos and locations to the whole world, but if you limit your followers I find HipGeo to be worthwhile for travelers with a preference for sharing.
HipGeo requires iOS 4.0 or greater. It is a 6 MB download. You can see some screenshots in the gallery below.