Google has let loose a new section of their Android developer portal -- Android Design. It's a site full of tools and suggestions to help application developers build apps that look and feel alike, following a sort of a style guide from the folks at Mountain View. Things like menu button location, and drawing windows and fragments should be done so that they "behave in a consistent, predictable fashion". We're not going to argue.
Besides all the helpful hints and guidelines, there's a special section for folks designing apps that are cross-platform. Suggestions like "Don't mimic UI elements from other platforms" or "Don't use bottom tab bars" will help Android apps look like Android apps, instead of rehashed iOS apps.
While these are all just suggestions, apps that follow them will look like they belong on an Android device. Conversely, apps that don't follow them will stand out -- and that's not always a good thing. Android should start to look awfully darn pretty from Ice Cream Sandwich forward -- I'd suggest everyone take a look at the links below and have a read.