Hi Raj
This is a very subjective question, when you say excellent & cost effective solution, any package you choose would have some pros and cons of its own, perhaps you need to evaluate them relatively based on your requirements
However you may have a look at the Microsoft Online Services and Solutions, however there are other partners too which offers hosted services
http://www.microsoft.com/online/default.aspx
http://www.projecthosts.com/
Hope this helps
Thanks | Sunil Kr Singh | http://epmxperts.wordpress.com