That last post got some good hits, and then I looked at my tablet, and realized I forgot a whole bunch of apps. I'll include the same categories, and list 10 more titles.
To get good reliable moving maps in most aircraft will take an external GPS unit. These external GPS receivers can be mounted somewhere with a clear view of the sky. Sometimes the tablets will be used in places where they are unable to get a full view of the sky, making them unreliable. The external GPS receivers may have other capabilities (IE WAAS or ADS/B) as well.
I forgot the biggest of the big names. Garmin has and Android app, Garmin Pilot. The tag line "Plan, File, Fly" is what it seems it can do. There is a 30 day trial with this app, and requires a $9.99 monthly subscription. It includes charts (VFR, low and high IFR, approach plates and airport diagrams. Gets weather from NWS, including METARs TAF, winds aloft, PIREPs and various maps. Allows flight plan filing via DUATs.
Avilution AviationMaps is another application that seems really nice for maps. Allows breifing and filing through DUATS. Advertises that it can get weather including NEXRAD through ADS/B receiver, making it a very handy tool. Can get weather maps, METARs, TAFs, PIREPs and NOTAMs while in flight, or on the ground. Icing, winds and area forecasts are only available on the ground (this is a ADS/B limitation, not the software). All the same maps, VFR, Hi/Lo IFR, approach plates and airport diagrams. The subscription is either $74.95/year or 149.90/yr premium.
AirNavigation Pro includes maps and instruments.The instrument looks like an HSI, which I have always preferred for telling me where to go, or if I am on course or not. The charts they say are free and cover the whole world. The cost is $26.95 to buy, and doesn't really mention any subscriptions. This may be an app to keep an eye on.
AirWX Aviation Simple layout, enter an airport, the tabs appear for METAR, TAF, PIREPS, Charts and Plates. A really simple thing to be able to check as you get to an airport, not sure how useful it will be when flying for a couple hours (doesn't say ADS/B receivers are supported). No subscription fee, but will cost you $6.99 to buy it.
Weather Pilot Simple organization, allowing looking at text weather for multiple airports at a time. Very light weight, seems pretty fast and reliable. Still limited to mobile data, and not ADS/B receivers. It is free, and no subscription is required.
Avilution E6B Flight Computer - Real basic conversions, but seems well organized. Enter what you know, and it will figure out the rest. It is $4.95 to purchase it. It is likely you will not be able to use this on a test, since the proctors will confiscate your tablet and phone before going into the testing area.
Trade-A-Plane I used this weekly for a while on my old phone. Really handy for looking up used plane prices, or avionics or whatever you used to see in the yellow paper. Loved it, but I am not looking to buy things these days, so sadly, I haven't used it in a while. This app is free.
Aviation Exam just had a huge upgrade, it is very pretty now. I most recently used their app to earn my AGI rating. The Flight/Ground instructor review was really helpful, and allowed me to get a good grade the first time. The app is free, but you need to buy the test you want to study from. The tests are mostly $9.99-13.12 for 2 months, and can be had in bundles (IE PPL, IR, CPL). The tests are for EASA and FAA. Hooks into http://aviationexam.com and allows sync'ing tests and results.
GPS Status isn't just for aviation, but if you use GPS for anything, it may give you more insight about the accuracy of your GPS receiver. It shows the receivers in the sky right and their relative position. On the bottom, it shows the relative signal strength in a bar graph. Most Androidn GPS receivers will allow picking up US GPS and Russian GLONASS GNSS satellite signals and use them to give even more accurate position reports. This will show most of the relative position information the device can provide, including error information (DOP/HDOP/VDOP and absolute error in ft).
Ultimate Flight Checklist Mobile is a huge name, and will put it in the bottom of any alphabet list, but it is a great checklist tool. It allows adding any number of checklists for various aircraft. It comes with the three popular training aircraft; Cessna 172, Piper Cherokee 180, and Socata TB-10. You may add your aircraft and customize the checklist for any particular aircraft. Set your checklists in a way that works for you and be safe.
This again is not an exhaustive list of the aviation apps out there for the Android. It is a collection of some that I have used, or thought were interesting. If you have a favorite, let me know, and I'll take a look. Authors, users, doesn't matter to me, I'd love to hear what your favorites are.