I am a big fan of open source software and Kdenlive is such kind of project. If you are looking for an open source video editor for linux distributions like Ubuntu, Fedora, OpenSUSE, Devian etc. and It also works on Mac OS.
Kdenlive is a powerful video editor where you can import and edit almost all the standard video files. Attach your camcorder with you computer and import the files from there. Now you can start editing video files thru Kdenlive.
Recently Kdenlive 0.7.6 released with some new features like Track Rename, Clip Management, Composite Transition, Cleaner User Interface and Mac OS Support. Below the step to install Kdenlive on Ubuntu 9.01 Karmic Koala.
sudo apt-get update && sudo apt-get install kdenlive
You can browse the tutorial for Kdenlive available on its website. As this is an open source project, you can also contribute to the further released of this nice video editor.
Share your favorite video editor (free or paid) thru comments. Windows users can use the DVD Live to boot their system with Linux and Use Kdenlive and then just exit. No need to install anything on hard disk. You may choose to boot the system using USB drive as well.