Detecting the default feed, for formatting

I probably just can’t think of the right terms to search on, so I apologize if this is a common question – just point me at the right post in that case.

I have a site hosted in WP with quite a few pages; our header.php has specialized code to set up menus based on which page is pulled. No problem for pages because I can set up a pgcategory and pgtitle custom fields, detect them, and build the menus based on those.

But, how do I detect when the basic front-page feed is detected? For one of the menus, I can just use the default ( } else { ) but on another one of them I need to detect it specifically, since it’s really not our front page but a sub-page of the larger site.

If you want to see it, this is for http://www.riverstoneschool.org. The front page of the blog will go under the Calendar and News section (but doesn’t right now because I can’t figure this out) to consolidate the “Press Archive” and “Updates & Announcements” items.

TIA for any pointers or suggestions!
-Matthew