Baraha used to be available free. But now they charge. According to my experience it is the best. The input has to be in Harvard-Kyoto script.

From: Patrick Olivelle <jpo@UTS.CC.UTEXAS.EDU>
Sent: Monday, 26 March 2012 7:56 PM
Subject: [INDOLOGY] Font

Dear All:

Can you recommend a font/program which would allow a Sanskrit text to be typed in Roman and to be converted immediately to Devanagari? I have noted some such programs Developed in India. Thanks.

Patrick Olivelle