The Play Store is great but there are good reasons to look at some other app stores as well for your Android phone or smartphone including better curation and deals.
GetJar
One of the oldest app stores in existence, GetJar has been catering to ecosystems as diverse as Java, Symbian, Windows Mobile and, now, Android. GetJar is still great to use because it regularly offers premium apps for free. You can download the GetJar apk to your Android phone and install it.
Amazon App Store
The Amazon App Store is well known to users who own a Kindle Fire tablet in which it is the default app store. The Amazon App Store runs a 'Free App of the Day' program which does exactly what the name suggests for paid apps. You can download and install the Amazon App Store apk to run it on your Android device.
SlideME
The SlideME app store can be accessed on your Android phone or tablet through the SAM app. SlideME is one of the best designed and good looking third party app stores out there. The app store also guarantees that every app you download is legal and safe.
App Brain
In a world with no Play Store, the App Brain app store could have easily filled the void. The store looks elegant and is very well designed for ease of use. App Brain also analyses the kind of apps you use and download to recommend new ones. You can download and install the App Brain app from the Play Store directly.
Opera Mobile Store
The Opera Mobile Store is another app store that caters to ecosystems beyond Android. However, it is quite suited for Android users because we've found that it's one of the best curated app stores out there. If you're looking for quality apps outside the Play Store, you should definitely go to the Opera Mobile Store website.