remm

This plugin provide widget that display a list with categories and posts in your sidebar. 
Widget can save the opened categories, and use cache.

Wp Ajax Tree

This plugin provide a widget that display a category and pages tree on your sidebar, using ajax to collapse categories.

burria

Creates a custom content type to upload pets, displays from 1 to 4 generations (parents are counted as first generation).
When you create a new pet it lets you select the mother and father and then draws a pedigree 
tree when the user is viewing the post.

Laika Pedigree Tree

This plugin creates a custom post type for pets, connected to his parents and then automaticaly draws a pedigree tree.

Wp Ajax Tree vs Laika Pedigree Tree