I always told my friends at university that Linux was good, and that it was better than Windows (for me), although I used the Microsoft operating system too. But as I stated on a previous post, I ditched Windows not long ago.
What has been quite surprising is that now five of my friends are using Ubuntu on their machines because Windows caused them too many problems, so they decided to give Linux a go. They liked it and are now using it, but take in account that they're computer science students, so they know their way around computers (in theory).
Other two friends are considering making the switch. They always ask me what Linux distribution they should install, and I always say "Ubuntu", simply because it works alright on most machines, and it's relatively easy to use and maintain.
These guys are somewhat knowledgeable about Windows, but one of then didn't even know how to partition a hard drive. Still, that didn't stop him and I helped him to install Ubuntu on his laptop. It worked alright, but the wireless network didn't work, and I told him I'd help him out later, but that he should search the Ubuntu forums and google to see if he could figure it out on his own. Today he told me he got it working and that made me feel good, because they're learning the ropes of a new system on their own.
The whole point of this post is that you can help the whole open source / free software movement by just using it. Sooner or later your friends or someone you know may become curious and discover this new world where (almost) everything is free, it works, and there is a big community of people willing to help you out with your problems. Not all is bad in the Linux world.