[Update] Those features in line tool has been integrated into NetBeans proper 6.x. So if you are running NetBeans 6.1 (the latest as of 5/2008), line tool plugin is no longer needed.
I use it everyday to copy and paste lines of text without using CTRL-C CTRL-V. This is its official description:
Line Tools Support following operations in text editors:
1. Move Line (or lines spanned by selection) Up
2. Move Line (or lines spanned by selection) Down
3. Copy Line (or lines spanned by selection) Up
4. Copy Line (or lines spanned by selection) Down
5. Sort lines spanned by selection in ascending order
6. Sort lines spanned by selection in descending order
7. Remove duplicate lines while sorting. Maintain the caret position, the selection and the order of start and end of the selection when moving/copying the lines.This is the first plugin I will install for every new NetBeans release. Unfortunately, NetBeans can't automatically migrate my installed plugins.
Oddly, this plugin doesn't show up in the official NetBeans plugin portal. The place to go is the author's (Sandip Chitale) blog.
You can choose either download the *.nbm file and manually install it, or add a new update center (Sandip Chitale's update center) to your NetBeans. After adding the update center, you will able to download a lot more good stuffs by Sandip Chitale.