Linux users have many of the same options as Mac and PC, but some more directed toward those who are interested in open source contributions. Programs like Jashaka are available on all three operating systems, but Kino is probably the best of the Linux-only realm. Though it is limited regarding what type of media it can log and capture, it does run quick and has a short learning curve.
When finding a freeware editing software it is best to decide exactly what your needs are and make decisions based on their specifications. If you need a complex system you are most likely going to have to sacrifice speed and ease of use. If you want to do a high number of small, simple projects with relative speed then you will probably have to cut down on the number of options the program will give you. Editing software, as with everything else on your home computer, is usually a trade off. But when considering freeware or open source software applications, you can't beat the price.