dev.Fishy

EN:
Adds a simple widget to the sidebar that displays a random posts.
RU:
Добавляет простой виджет в боковую панель сайта, который отображает случайные посты.

RandPost widget

There are times when you’d like to have a certain type of post appear in a widget for use in your sidebar or (in some themes) your header or footer.
I used this to display a random senryu on each page, but it will work equally well for any group of reasonably small posts.
There is the option to include the title of the post, the title of the widget, both titles, or neither.
If you want you can add a bunch of widgets, each showing up to five random posts from a different category.

Random One Cat Widget

This Widget shows up to five random posts from a given category

RandPost widget vs Random One Cat Widget