Blushing Boy, a web shop for sellers and buyers. Of home-made and self-designed Arduino electronics. And its ilk. It’s Malmö-based. This is awesome stuff. You can buy a Smapler there.
Programming Interactivity: A Guide for Processing, Arduino, and OpenFrameworks, 1st Edition as a Rough Cut. Their pricing model is interesting – if you’re very curious, but also want the book – you can pay more now for early access. Most people are both curious but want the paper book.
If you’re into this stuff, come to the local hackerspace. Bring your stuff.