Yelp for the iPhone introduced Check-ins back in January and while the Android app doesn't have that (yet -- Yelp says it is coming soon), the new additions are still pretty cool.
The first big new feature is that you can now bookmark businesses with the Yelp Android app or on Yelp.com and those bookmarks will be synchronized across your account. That's really cool because that way if you find something on your phone, you can check it out in more detail online and vice versa.
While Yelp doesn't currently allow publishing of full reviews from mobile devices (the Yelp blog explains why), you can now create draft reviews in the Android app, which means that once you get back to your main computer, you can fix any spelling errors or make other types of corrections before publishing.
