Checked out your site and as an avid backpacker found the idea pretty cool, but yes, it feels empty.

My experience is that backpackers tend to use Facebook a lot, so integrate your login with Facebook Connect for starters. Make it more social by hotels/restaurants/etc. having Like buttons that points to your site.

Create a Facebook group, where these people can get to know each other. It is also a good opportunity to advertise your page.

Try to fetch data from Google Maps/Yelp/Foursquare and put it on your site. Make badges and achievments like Foursqare does, that users can earn and show off. That makes them wanting to go back to your site and make activities.