Nobble

This should work, back up before trying though.

Add this to functions.php (located in p2’s theme directory).

/* the following tweak filters the front page to only contain a single category of choice */
add_action('pre_get_posts', 'front_page_cat_filter' );

function front_page_cat_filter()
{
  global $wp_query;
  $cat = get_cat_id('post');
  if( is_home() || is_front_page () ) {
     $wp_query->query_vars['cat'] = $cat;
  }
}
/* end of tweak */

then in ajax.php, on line 245 in the most current version of p2 inside the ‘get_latest_posts()’ function, find the line:
query_posts( 'showposts=' . $num_posts . '&post_status=publish' );
and replace this with:

/* tweaking the updated posts to only include a certain category */
if (is_home () || is_front_page () ) {
query_posts( 'showposts='. $num_posts . '&post_status=publish&category_name=post');
}
else
{
query_posts( 'showposts=' . $num_posts . '&post_status=publish' );
}
/* end of tweak */

Depending on the category you want to show, you have to replace the word post with your desired category (so…category_name=<type your category here>) and get_cat_id(‘<type your category here>’)

I haven’t tested this extensively but it should establish what you want to do.

* made a few small corrections since posting this

P2 child themes work great when all you have is css/layout tweaks and some basic addons that don’t change the basic p2 functions. Other types of edits such as these can get messy and it kind of defeats the purpose of easy updates because it introduces a hassle to make everything work. P2’s a theme that gets continually updated so if you’re making significant changes you can easily either break your theme or lose out on updated code. If you go with flamenco’s solution for example, if a future p2 update includes changes to the original options-page.php file, you’re missing out on it (and it could break your theme if other updated code relies on the changes).

I hope the great folks behind P2 think about making substantial customization more user friendly. Some ideas are adding hooks, converting part of P2’s functionality into a plugin or putting together more theme settings options that cover popular features such as category selection and giving users more control over what boxes/post types appear.

As it stands sometimes it’s more convenient to forgo theme updates when you have made significant modifications, which is only fine as long as there are no security holes needing to be plugged/or bug fixes needing to be corrected.

sorry I didn’t paste what needs replacing in its entirety,
as of the latest version the lines 195+196, comment them out:

$accepted_post_cats = apply_filters( 'p2_accepted_post_cats', array( 'post', 'quote', 'status', 'link' ) );
		$post_cat = ( in_array( $_POST['post_cat'], $accepted_post_cats ) ) ? $_POST['post_cat'] : 'post';

and replace with
$post_cat = $_POST['post_cat'];

it’s not the only change you’ll need to make as you’ll need to pass on what the default category is as well either by changing the submit form and associated code or doing a bit of a hack, for example:
if ($post_cat == 'blog ') { $post_cat = 'yourdefaultcat'; }

One way of doing it is adjusting the following line in ajax.php

$post_cat = ( in_array( $_POST['post_cat'], $accepted_post_cats ) )

to

$post_cat = $_POST['post_cat'];

or you can add your desired category to the list of accepted post categories, the problem is that it is hardcoded into the theme and thus the manual tweaks in the code. Maybe in a future version they can add some more options and flexibility to incorporate more usage scenarios.

This can be done, it’s not too hard…Nice idea, reminds me of the good ol’days when incoming emails prompted sound notifications (although outlook still has it).

here is probably the most informative thread regarding categories + p2 so far, had you checked it?
http://wordpress.org/support/topic/dropdown-category-selection-for-publishing-posts-in-p2-theme-v113

stoupon, do you still want a look at the code or have you settled on a different solution?

I’m doing some work on my theme this month and picking up development again when I get back from a 2 week trip. Cool new part: producteev integration.