Open up your skin1/customer/home_main.tpl
You'll see a wack of conditionals using the $main variable. You could implement similar things in home.tpl
For example:
Code:
{if $main eq "register"}
We know we are on the register page
{/if}
{if $main eq "product"}
We know we are on a product page
{/if}
{if $main eq "catalog"}
We know we are viewing a category
{/if}