Here are most of the important apps for the Android operating system. Sensei's Library  contains more details about these and other apps.
These are in English and all allow users to interact with other users, players and games on the servers they support. They are all free and require you to get an account before you can use them.
Most of these also allow for game recording and editing
Gobandroid  is a fully featured game recording program that comes in two versions, Tiny and HD with slightly different user interfaces. You can also load games and problems from online sources, through helpful links in the program itself, and can install the gnugo AI  if you want to play against a computer.
WegoIgo  has a one touch stone placement. It loads problems and professional games, cleanly and easily, and you can download the AI if you want to play against gnugo. It also loads Kogo’s Joseki Dictionary. There is a free version and a paid for one (£1.99). It offers advanced SGF editing features to boot, and you can comment and mark games up for study. Although the free version includes all of the features, there is a paid version ($2.49) for faster updates.
ElyGo  play against your computer (GnuGo). Includes built-in professional games and problems with answers as well as bad variations, playing and observing games online on Pandanet-IGS, SGF editor and loads Kogo's Joseki Dictionary. There's also a free version (£3.99).
Champion Go ～Crazy Stone～  is a strong Go playing engine (4 dan?), with different playing levels and an SGF viewer. (£3.16)
Go  plays Go on 9x9, 13x13 and 19x19 boards using the Aya engine. There's also free version. (£2.99)
GOdroid  play games against your computer (8-12 kyu). Also allows two players to play against each other. (free)
Silver Star Igo  play against your computer. Also allows two players to play against each other. (£4.50)
These are mainly for problem review and solving:
GoGrinder  problem practice. (£0.63)
GoEdit  records and edits game records. (£0.61)
The Gobandroid, WegoIgo and anDGS information is abstracted from the American Go E-Journal review in July 25, 2012 .