There are different type of keyboard layouts to type Marathi contents. Many of us are practising for years with the some of the following keyboard layouts.
You can get the information and keyboard installer file at http://kolhapur.nic.in/new/Howto_UNICODE.html
For Phonetic typing use can use Google Marathi Input Tool.
You can download it from http://www.google.co.in/inputtools/windows/