After "Agninakshatram", "Mohanam" raaga gained immense popularity on account of "Ninnu Kori". I will not get into the details the how, what and where of raaga - simply because Uttara has done such a fabulous job - and any of my explanations would pale in comparison.
Listen to Ninnu Kori from U Srinivas of the Mandolin fame. This one is my personal favourite when it comes to rendition of Mohanam. (You must have either Real Player or Windows Media Player to listen to this - it will pop up in a new window.)
Here's the song from the movie.
... and last but not least Raag Bhupali the equivalent of Mohanam.