Macintosh provides unicode fonts and keyboards for many Indian Languages since the introduction of Tiger. The language support is built into the operating system itself. The indian languages Tamil, Sanskrit, Hindi, Marati, Bengali etc. are supported. Textedit, Keynote, Pages, Mail, Filemaker pro and many other software support these unicode fonts. It is possible now to send email in tamil or hindi or sanskrit using the email clients Mail and Entourage. Thunderbid also supports this scheme.
The operating system comes with a Tamil unicode font Inaimathi and supports two keyboard options, namely Anjal (almost phonetic) and Tamil99.
To activate the support for Tamil Language,follow the following procedures.
Step 1. Open System Preferences
Step2. Click the International Option in personal section
Step 3 Click on edit List under Languages Menu
Step 4: Tick the desired language and click ok to go back to International menu
Step 5
Click on Input Menu and choose the Anjal and Tamil99 input Method
Step 6. Close sytem Preference menu.
To use the Tamil keyboard and font in textedit first open the text edit application and then click on the american flag icon
on the upper right corner in the menu bar and choose Anjal from the drop down Menu. (optionally the keyboard also can be chosen to get a virtual keyboard.
The American flag will turn into 
Now start typing the following key sequence
agara muthala ezuthellAm aathi pagavan muthtrRE ulagu
this will appear on the textedit
அகர à®®à¯à®¤à®² எழà¯à®¤à¯à®¤à¯†à®²à¯à®²à®¾à®®à¯ ஆதி பகவன௠மà¯à®¤à®±à¯à®±à¯‡ உலக௠(the font is Inaimathi a unicode font).
To switch back to english click at the same anjal symbol (on top right corner) and select US. Thus by clicking on the US symbol one can type in various languages in the same document
Devanagari-qwerty can be chosen in the same manner to type in sanskrit. The Devanagari keyboard layout is as under (pdf here):