Tools Customizing Kindle (plugin or some such)

Hi,

I am new to this forum and the Kindle world. I have got a Kindle Touch, and I feel a need of customizing it.

Could someone please guide me to some threads/forums/websites that can act as a good reference points for plugins/add-ons or some such things for Kindle?

My initial search is not leading me to any good concrete place.

Thanks,
Mukesh