Writing in Bengali
As explained elsewhere, Bengali unicode text consists of a sequence of 16-bit unicode characters, which are stored in 8-bit files in some sort of encoding. To create such a file, it's usually convenient to use some sort of high level processing software such as a text editor.
In the case of Bengali and similar languages, there are two popular approaches for text input. One is phonetic input, which means using the standard English keyboard to type `romanized' versions of the Bengali words one wants to write. For example, বাংলা could be typed in as `baaMlaa'. This can be thought of as a special case of methods which are not necessarily phonetic in the above sense, but are sophisticated enough to permit multiple-key sequences.
The other approach is to define a new leyboard layout, which for all intents and purposes replaces your English keyboard with a Bengali keyboard, with one key for all Bengali unicode codepoints. The choice of mapping is arbitrary, and may or may not have any relation to phonetically similar english keys. It's usually possible to switch between layouts quite easily.
Pros and Cons
Either of these two approaches may suit you better, you should try out both before deciding. Unfortunately, these two are not equally accessible. Changing the keyboard layout is obviously much easier at a system level, and with a little bit of work, one can set up one's system so that one can easily switch to and from a Bengali keyboard layout. When in Bengali mode, it would be possible to type Bengali in any software.
Phonetic input, on the other hand, is usually software specific (I don't know if it's even possible to do at a system level).
Another completely independent concern is whether your software can display Bengali properly at all. It's not much fun to write Bengali and not being able to see what you are writing.
We will first discuss some software specific solutions before moving on to system-wide keyboard layout based solutions.
Software specific methods
Yudit
If you are working on a system with no Truetype font support (such as older versions of GNU/Linux or Unix), your only option is probably Yudit. Even on up to date systems, it's a very flexible and powerful text editor. It's available for Windows as well as X based systems. The only downside is that its look and feel is a bit dissonant and it's slightly difficult to customize. Let us know if you would like us to put a brief tutorial on how to set up Yudit for Bengali.
Lekho
If you do have Truetype support (but not necessarily support for the advanced opentype features required for Bengali), Lekho (also a subproject of Ankur) is a good option. It uses Qt, so works on most platforms. It uses Unicode for storage, but renders glyphs using a special Trutype font (internally reproducing much of the work done by an Opentype renderer).
Javascript
If you have Opentype support (for example, if you can properly view the contents of the Bengali Archive in a web browser), you could use the following Javascript pages. This requires only a web browser, and you don't need to download any other software. This is not very useful for long term use, but will get you a feel for phonetic input.
- Converter: The first page converts a given bunch of romanized text into Bengali.
- See as you type: This is a more WYSIWYG type thing where you convert one word at a time, and you can see each word in Bengali as you type it.
Both of these pages can be downloaded and saved on your computer, and subsequently used offline. Click on the `Don't Panic' button for help on usage. To save the output generated by these pages, you need to copy and paste it into another editor, presumably one without Bengali input support, such as Notepad, since otherwise there's no point in using this :-)
System specific methods
GNU/Linux
Detailed instructions are available here.
Windows
Microsoft officially doesn't support Bengali yet, but reportedly will in the near future. Links to a few alternatives are given below, which Windows users may find useful. Note that not being a Windows user myself, I have no idea how well they work or how they are licensed.
Feel free to send me any more links that you think should be here, or even better, a review of what options a Windows user might have.