Michael Adams (mdawaffe)

Just One Category will cause WordPress to display on a category archive page 
only those posts which are direct members of that category, i.e. this plugin 
will exclude from that category page all posts which belong to any of that 
category’s subcategories but do not belong to the category itself.

Just One Category

On a category's archive page, displays only the posts directly in that category, not in any sub-categories.

sembee

A basic plugin that excludes posts published before a given date from appearing on the front page. This can be useful if you want to “reboot” your blog but don’t want to lose all previous posts and break all links to them.

Front Page Exclude By Date

A basic plugin that excludes posts published before a given date from appearing on the front page.

Just One Category vs Front Page Exclude By Date