Grantha

There are around 5 fonts for Grantha: e-Grantamil,Code2000, IIT-M Grantha Font, Ganapathy & Kunchitapada.

Out of those 3 are Truetype, 1 is Opentype, and 1 is encoded in PUA.
Ganapathy & Kunchitapada fonts are very early fonts created around 1998, so they are not exactly very aesthetic in appearance. Both have the same Layout, therefore text composed in one font can be switched to the other without any loss. They don't yet have a associated Keyboard Input method.