@Bamboleo: It's available for exactly 13.71€ as direct download from the developer's site which is linked in my sig picture.
A very nice retail version of Machinarium (which includes the soundtrack on an extra audio CD, Samorost 2 and a poster) was only released in Germany so far as far as I know:
http://www.amazon.de/EuroVideo-Bildprogramm-GmbH-Machinarium-Samorost/dp/B002PAR4CU/ref=sr_1_1?ie=UTF8&s=videogames&qid=1264451248&sr=8-1
(I bought the retail version as well to support the developer.)
"European" retail version of Machinarium will be released in March:
http://www.mcvuk.com/news/36894/Mamba-Games-dates-H1-2010-titles