Hi,
Nice to see this post from another tamilian as i am also a tamilian . More nice is i have solution for your problem. I assume you want to read tamil article found in the Internet like dinamalar, ananda vikatan, etc. If this is the case then you do not need to install any tamil fonts to read it. Here i assume you are using firefox as the default browser, as its the case in ubuntu. Then all you need to install is padma. Padma is an extension to firefox that allows you to read tamil text without installing fonts. Padma is installed in firefox & not to your system. You can find padma froom this url
http://padma.mozdev.org/ . Also you can type in tamil with scim. For installing scim use synaptic. Install tamil locale with synaptic. Good thing about scim is, if you select tamil phonetic, then you dont have to know tamil typing to type. You can type tamil in english & it will appear in tamil For example typing ammaa will appear as அம்மா. Hope you enjoy the tamil experience with ubuntu
--ashwin