For MSFT Windows platform, there'r lot of resource in official press.
For Linux/BSD, lot of resource on internet but need some trivial/introduction article for green hand.
For WIN/PC Green hand:
1. Prepare VMWare/Virtual PC.
2. Get Linux/BSD bootable CD.
3. Install kernel source tree for pratice.
4. Get Start on device driver.
Here is a article, that's very simple and trivial...
Find something/projects, you may interested
i.e:WiiLi, Linux for Wii
5. Find a new job you have chance to use these stuff :-)