Sanskrit is an ancient Indian language made up by Northern Indians (Aryans). Latin is considered "dead" or "half-dead" today, but Sanskrit was always a "dead" language. That means that it was never spoken like an everyday language; it was only used in literary works. (I don't know if anyone ever spoke Manipravalam or Pattu.)
However, Indians think of people as scholars if they can speak Sanskrit, the same way that Westerners think of people as scholars if they can speak Latin! Sanskrit is found in all of the Hindus' holy books--the Vedas, Upavedas, etc. as well as some Buddhist works (I think!).
Strangely enough, Deutsche Welle is the first radio station in the world to broadcast in Sanskrit! Unfortunately, it seems as if they no longer have the slightest trace of it.
However, if you want to learn Sanskrit first, there ARE links existing for that! You can go to http://www.omniglot.com/writing/devanagari.htm to learn the Devanagiri script in which Sanskrit is written and/or maybe you may want to take a look at http://acharya.iitm.ac.in/sanskrit/lessons/lessons.html, where you will find a pretty good Sanskrit course.
People may think that Syriac is a "dead language," since it is "only" used in Syrian Christian churches. However, that is very incorrect, since it is neither "dead" nor a language!
Syriac is actually a dialect of Aramaic, the language of the Assyrians and Aramaeans in the Bible. Therefore, it was never a language in the first place.
And it isn't dead, because after the Assyrian Empire collapsed, the Assyrians' culture survived even though their era of persecution apparently began! They supposedly were especially persecuted when they converted to Christianity. :( To learn more, go to http://aina.org/martyr.htm. (You might say they're lying or that they just want regional autonomy and power. You might criticize them in some other way. Well, maybe you're right, how should I know!?)
Syriac is the Eastern dialect of Aramaic, spoken around Kurdistan (basically the border around Turkey, Iraq, Iran, and Syria) where the Kurds, an Indo-European people, live. Though Aramaic was originally basically the Aramaeans' language, Syriac has more of the ancient Assyrian language incorporated into it. The other dialect, apparently spoken around Palestine and the surrounding areas, is called the "Palestinian" dialect; this dialect seems to be strictly Aramaean!
If you are interested in learning Syriac, http://members.aol.com/assyrianme/aramaic/aramaic.html is not bad, though a little more vocabulary and such would do!
Tamil is spoken in Tamil Nadu, just east of Kerala. Basically, it shares a border with Kerala's South and Central regions. Like Syriac, it's not a dead language and it's veeeery old! To find out more about Tamil Nadu (such as its exact location) go to http://www.india-tourism.com/en_tam.0.html.
Though they use a slightly different script (which was easy to learn for me!), it is very similar to Southern/Central Malayalam. For example, if I was in Kerala and suddenly somebody out of nowhere came up to me asking in Tamil, "vaNakkam aiyya, neenggal enggu chelkirriirgaLaa?" I would know that he is asking me where I'm going. (This is similar to Malayalam "ningngaL engngOTTu pOkunnu?" The word "chelkirriirgaLaa" is more similar to the Malayalam word "chellunnu," but in the given context, it doesn't translate so easily!)
To see Tamil script, go to http://www.omniglot.com/writing/tamil.htm. If learning this ancient language (does anyone know exactly HOW ancient it is???) is your ambition, visit http://tamilclass.com/.
Kannada is spoken in Karnataka, just north of Kerala. It borders Northern Kerala in general. That's why Malayalees from Northern Kerala seem to understand Kannada better than Tamil. You can go to http://www.india-tourism.com/en_kar.0.html if you want to find out more about where Karnataka is.
Kannada's script is VERY different from Malayalam's (see http://www.omniglot.com/writing/kannada.htm) ! As the above link about Kannada script mentions, it's much more similar to Telugu, spoken near Karnataka.
Karnataka was more associated with North India, since it's one of the only two states in South India that border North India. It's also the only state that managed to attack Kerala. (The famous Tipu Sultan, former king of Karnataka, apparently marched on part of Northern Kerala, even though he had to cross mountains to do it.)
Unfortunately, I haven't found a good course for Kannada with the script. I'd be more than happy if someone could tell me where to find one!