Here is a short list of free apps, in no particular order, that are useful for life in Japan.
Google Maps with PC-based "my maps"
maps.google.co.jp is still in "beta," a term I put in quotes because many of google's products seem to be in a perpetual beta state. Often, multiple searches are required, which is a bit of a pain to do from a handset. So, whenever possible, I prefer to search from a computer and save locations. These can be loaded onto your phone from layers > more layers > my maps (see photo).
Google recently introduced walking direction for Japan, but if maps is in beta, these directions are in alpha, though they are essentially correct. Just don't try and cross six lanes of traffic on foot outside of a crossing.
Bump
When it comes to Android in Japan, one of the most common complaints is the lack of infrared for transmitting contact information. Bump provides an option, as long as the other person is using an iPhone, iPod Touch, or Android phone with Bump installed. Unfortunately, the Android port does not include all the features of the latest iPhone version.
One of the things I don't like about infrared is that you cannot choose which of your personal information to share, but with Bump, you can. However, Bump won't work unless you have an internet connection. Bump encrypts your data and routes it through their servers to the other person's device, so if you are uneasy with a third party handling your personal information, then perhaps you would prefer a different option.
QR我風 (QR gafu???)
I'm not exactly sure how to read this, but it is another option for transmitting contact information without an infrared port. The app displays a QR code on your screen that the other person can simply scan. Your profile is not chosen from your contacts list, but rather manually entered. You can register two different profiles, each with a separate name, phone number, email, and website address.
This app has the advantage over Bump in that it does not require an internet connection and can be used to transfer data to a standard Japanese cell phone. If the other phone is capable of displaying a QR code, this app can also read in contact information.
Jorudan（乗換案内）
There are a several free apps for getting train directions. Most of them are a simple front end for accessing either google or goo. Jorudan offers the only free self-contained app, which also has more features than the others. While it doesn't give you the option to save a list of frequently used stations, it does save a long history, making recalling stations fairly simple. It also allows you to specify connecting stations and is the only free app to provide schedules for individual stations. Schedules can be displayed in multiple formats, including departure and arrival time.
While the app provides train delay information, the live feature is a real time feed regarding what other users are reporting (see photo). It often happens that a train will be delayed but no official notice is published.
Traffic Status（渋滞状況）
If you get around by car more than by train, this app provides realtime expressway traffic information from the
Japan Road Traffic Information Center.
World Weather Clock（世界天気時計）
This is a nifty widget that sits on your home screen and displays weather information for any city you choose. There is an option for a large widget that takes up two spots on the home screen, as well as a small widget that only takes up one. In the large widget, additional information can be displayed, such as the local time. Clicking the widget will pop up a five day forecast.
The coolest feature of this app is that you can set a widget that displays information for your current location based on GPS. You can manually update your location by clicking the widget and choosing update location.
Japan Weather Radar（日本のお天気レーダー）
This app displays current radar (as well as 3 hours previous) from the
Japan Meteorological Agency, part of the Ministry of Land Infrastructure Transport and Tourism.
Simeji
This is an alternative to the iWinn IME that comes with Docomo's HT-03a (HTC Magic/Sapphire MyTouch 3G). I find it to be more responsive than the default IME. However, it does not have as extensive a dictionary. It was originally developed to give Android users a means for inputing Japanese before the first Android phone with a native Japanese IME was released. At the time, it used a social IME to convert phonetically input characters to Kanji. Now, Simeji uses OpenWnn for character conversion. It also retains the social IME function, which can be accessed by pressing the mushroom button in the list of suggestioned conversions. The main reason Simeji is popular with Japanese people is because it contains "flick" or "hanabi" style input for Japanese. When flick is set as the input method, pressing a kana character on a keyboard pops up all the additional characters in the group (if that makes sense - pressing あ will pop up い う え and お in a shape reminiscent of fireworks).
Simeji also contains a launcher that allows you to quick launch preset apps by pressing the trackpad and flipping the phone up down right or left (see photo).
ImoNi（芋煮）
This is used for inputting emoji, but you need to be
subscribed to imode.net.
QR Code Scanner（QRコードスキャナー）
It's Japan. Everyone needs a QR code scanner.
My Docomo Checker
Simple app for checking your cell phone usage from your phone.
