They asked me a bunch of graph theory / number theory problems, if you didn't know the algorithms and could implement them quickly you'd be SoL.

For me programming challenges were my way to get a foot in the door without a degree. I remember getting interviews from Google after their first Code Jam. And facebook after I solved a bunch of programming puzzles they released. But topcoder was my real salvation from my parent's basement.

Even though I have a career now, I find solving them lots of fun. Sometimes I come to the solutions when I'm drowsy before bed and have to get up and write it down before I forget!

Project Euler

UVa Online Judge

Kaggle

TopCoder

facebook put me through a 5 hour whiteboard test. 1 engineer each hour interviewed me. I was exhausted afterwards and slept the entire flight home.

I tried OpenBSD on a new Dell laptop. I thought I would end up writing over it, but I experimented and found that it is awesome. Everything I want is working: encrypted home partition, sound (hd-intel), 3d hardware accelerated graphics (intel card), suspend, wifi internet (with a tiny dongle), my wireless mouse, touchpad. all of my favorite applications are in ports and chromium is working fine. After all that I ended up keeping Openbsd as my desktop. It feels much cleaner, I like how everything is organized. Of course it can't use as many devices as linux. YMMV