There are a lot of fonts of Tamil are available. These font have very glyphs to display and print in Tamil Language. With fonts you can use keyboard driver software which feature to work on different keyboard layout e.g. inscript, phonetic or typewriter.
Unicode Typing Tool:
This is a typing software which let you type in Tamil and other Indian Languages. Download Typing Tool
Microsoft Indic Language Input Tool for Tamil
Microsoft Indic Language Input Tool helps you enter Indian language text easily into any Microsoft Windows applications. The primary input mechanism is transliteration. Additionally, it provides a visual keyboard to assist with editing words that do not transliterate properly. Download Microsoft Indic Language Input Tool for Tamil Language